The beam waist of the focused laser beam controls both the track pitch
and the density and size of the small pits which encode the data and
make up the track.
For the purposes of this project you may assume that the track pitch is
0.8 times the beam waist.
The linear data density (data per unit length of data track) depends on
the size of the pits and how closely they are packed together. These
dimensions are also controlled by the resolution of the focused laser
beam, i.e., the beam waist. Values for linear data density are listed in the
last column of Table 1 for infrared, red and blue laser technologies.
Linear data density is discussed further in section 7 below.