Patent ID: 6285402
Filing Date: 2001-09-04
Classification: G09G,H04N

Abstract:
A scan converting device for converting the scanning frequency for an analog input image signal and for outputting an image display signal, comprising:a first PLL circuit for creating first clock pulses synchronous with said input image signal;an A/D converter for converting the input image signal into a digital signal by using said first clock pulses;a primary processing circuit for processing said digital signal by vertical interpolation;memory for storing the digital signal processed by said primary processing circuit;a secondary processing circuit for reading the digital signal corresponding to said input image signal from said memory and for adding an asynchronous horizontal sync signal and an asynchronous vertical sync signal to the digital signal;a second PLL circuit for creating second clock pulses and having clock frequency variable means for changing the frequency of said second clock pulses; anda D/A converter for converting the digital signal processed by said secondary processing circuit into said image display signal by using said second clock pulses; the horizontal size of said image display signal being adjusted by changing the frequency of said second clock pulses by said clock frequency variable means and by accordingly changing the ratio of the effective image period relative to one horizontal period.