1. Field of the Invention
The present invention relates to television displays and the control thereof. More particularly, it relates to television displays with progressive rather than interlaced scan.
2. Description of the Prior Art
As is well known, television pictures are generally generated by interlaced scanning; i.e., for each pair of fields constituting a frame, each line of the second field is positioned in space between successive lines of the first field. This is illustrated in FIG. 1A. In this figure, as in FIGS. 1B and 1C, an edge view of the scanning lines shown, the arrows depicting light intensity. It will be noted that the interlace pattern illustrated in FIG. 1A results in interline flicker which becomes increasingly annoying as the size of the display is increased. On the other hand, in FIG. 1B a progressive scan utilizing and adjacent line averaging algorithm is illustrated. In a progressive scan, a line is interpolated between two successive scan lines within each field and horizontal scanning takes place at double the interlace scan frequency. The problem of interline flicker has been alleviated, but, as will be noted in particular where the light intensity changes from maximum to minimum, namely at the top and bottom of the lines displayed in FIG. 1B, there is smear in the vertical direction, i.e. sharp contours are destroyed. Finally, FIG. 1C illustrates a progressive scanning algorithm in which the interpolated lines are simply repeats of the previous line. It will be noted that the pattern is stretched in the vertical direction, while interline flicker is still present.
In addition, more complex and expensive methods of processing the interlace signal to create the progressive scan display are known. These require motion detection means if an acceptable picture is to result.