I specified purchasing a focusable laser diode, because the “focusable” lens is (typically) removable, see figure 1.
Figure 1 - Focusable Laser Diode
The lens collimates the laser light into a beam, and produces a dot, when pointed aimed at a white card. When we shoot holograms we do not want a dot, see figure 2.
Figure 2 Laser dot produced from laser diode with lens intact.
We want the laser light from the diode to spread out as much as possible so we remove the laser diode lens entirely, see figure 3.
Figure 3 Removing lens from laser diode
The following image shows the laser diode output without the lens, see figure 4.
Figure 4 laser diode illuminating white card with lens removed