Convergence, RPTV

[Richard]

RPTV or FPTV consists of three seperate pictures of red, green , and blue and when they are all on top of one another they form a complete picture at the highest resolution. Performing this alignment is called resgistration and this is done by manipulating the convergence circuits which force the beams to the particular positions on the screen. Normally only red and blue are matched to the green and green is the reference color for all issues concerning geometry, linearity and overscan.

Convergence is magnetic field sensitive and that is why it can only be perfected for a single direction in reference to magnetic north. If I could put you and your display on a lazy susan and spin you around while looking at a center cross you would see the RGB components moving about. The auto focus systems on the market do a good job of getting things close which is good enough for the mass market but it can be better. These circuits basically have light sensors around the frame that feed back the positions of the light striking them to computer which then adjusts the convergence on simplistic levels to correct errors. On most systems you train the computer what a correct convergence is after someone has performed registration or convergence. I have found that after I have done my job and then perform auto convergence it throws off my work causing me to go through the process again. At this time I recommend after calibration that the customer not use this feature unless necessary. If the TV gets moved to a different location compare the convergence using Avia before and after. Based on what you see you may very well find that using this feature improves things.