Waveform generator

A waveform generator comprising:

• a first memory having a function data corresponding to a bisymmetrical output;
• a counter for sequentially counting screen position;
• a second memory for sequentially outputting data which is synchronized to the output of said counter;
• and
• a processor which produces a corrected position signal by adding and multiplying the function data read out from said first memory using preset position information corresponding to each position on the screen, an offset coefficient, and a scanning frequency correction coefficient;
• said corrected position signal is used for reading out the function data from said first memory again so as to produce an at least substantially bisymmetrical dynamic focusing output data by multiplying said function data by an amplitude coefficient;
• and said dynamic focusing output data is written to said second memory.

A method of generating a focusing waveform for a display, comprising the steps of:

• applying a predetermined function to a position signal which corresponds to respective screen positions of said display to obtain a corrected position signal;
• performing a plurality of mathematical corrections to said corrected position signal;
• and
• performing at a least one of said predetermined function and a further function to said corrected position signal to obtain said focusing waveform,
• wherein said predetermined function and said further function provide an at least substantially bisymmetrical output.

A method for generating a focusing waveform for use with a display, comprising the steps of:

• applying a first bisymmetric function to a position signal corresponding to screen position on said display to obtain a modified signal;
• adding a correction to said modified signal;
• applying a second bisymmetric function to said corrected modified signal;
• wherein said first bisymmetric function and said second bisymmetric function each provide an at least substantially bisymmetrical output.