A gradation circuit is provided with an error diffusion circuit, a dither pattern circuit and a switch. The error diffusion circuit converts a digital signal into a signal indicative of a level of gradation by an error diffusion method. The dither pattern circuit converts a digital signal into a signal indicative of a level of gradation by a dithering method. The switch selects for output between an output signal of the error diffusion circuit and an output signal of the dither patter circuit as on output signal of the gradation circuit.
1. A display device comprising:
a first input terminal for receiving an analog image signal;
a second input terminal for receiving a digital image signal;
an analog-to-digital converter connected to said first input terminal;
a first switch for selecting an output between a digital signal outputted from said analog-to-digital converter and a digital signal inputted to said second input terminal; and
a gradation circuit for converting a digital signal outputted from said first switch into a signal indicative of a level of pseudo gradation, said gradation circuit comprising:
an error diffusion circuit for converting said digital signal outputted from said first switch into a signal indicative of a level of pseudo gradation by an error diffusion method;
a dither pattern circuit for converting said digital signal outputted from said first switch into a signal indicative of a level of pseudo gradation by a dithering method; and
a second switch for converting for output between an output signal of said error diffusion circuit and an output signal of said dither pattern circuit.
2. The display device according to claim 1 , wherein said first switch is operatively switched by a user.
3. The display device according to claim 1 , wherein said second switch is operatively switched by a user.
4. The display device according to claim 1 , wherein said gradation circuit comprises a noise detector for detecting noise of an output signal of said first switch, and a switch controller for controlling said second switch in accordance with a result of detection by said noise detector.
5. The display device according to claim 4 , wherein said noise detector determines whether lower bits of an output signal of said first switch include noise or not.
6. The display device according to claim 5 , wherein when it has been determined by said noise detector that noise is included, said switch controller causes said second switch to output an output signal of said error diffusion circuit.
7. The display device according to claim 5 , wherein when it has been determined by said noise detector that noise is not included, said switch controller causes said second switch to output an output signal of said dither pattern circuit.
8. The display device according to claim 1 , further comprising:
a driver for receiving an output signal of said second switch; and
a display panel to be driven by said driver.
9. The display device according to claim 2 , further comprising:
a driver for receiving an output signal of said second switch; and
a display panel to be driven by said driver.
10. The display device according to claim 3 , further comprising:
a driver for receiving an output signal of said second switch; and
a display panel to be driven by said driver.
11. The display device according to claim 4 , further comprising:
a driver for receiving an output signal of said second switch; and
a display panel to be driven by said driver.
12. The display device according to claim 5 , further comprising:
a driver for receiving an output signal of said second switch; and
a display panel to be driven by said driver.
13. The display device according to claim 6 , further comprising:
a driver for receiving an output signal of said second switch; and
a display panel to be driven by said driver.
14. The display device according to claim 7 , further comprising:
a driver for receiving an output signal of said second switch; and
a display panel to be driven by said driver.
15. A video display device capable of receiving a digital video signal converted from an analog input video signal and a digital input video signal, said display comprising a gradation circuit wherein:
a pseudo intermediate gradation process can be executed in both an error diffusion method and a dithering method, and
when said digital video signal converted from said analog input video signal is input, said pseudo intermediate gradation process in said error diffusion method is selected, whereas when said digital input video signal is input, said pseudo intermediate gradation process in said dithering method is selected.