pinball1970 said:
"I thought that Floyd's visual show was a little laser focused, they should have more back drop videos like they had in the 60s.
Make it real man."
Makes total sense.
I think
@Bystander was referring to the nature of "normal" laser light. An intense small dot of light with all the photons going in parrallel. Focusing not usually necessary.
There are however cases where you want focused laser light. for example
confocal scanning laser microscopes have produced big advances in modern microscopy.
Putting the laser light through a lens (focusing it) allows you to generate images in various ways. The confocal mechanisms allows you to more easily assemble a clean 3D image, and being digital goes right into computers for 3D imaging. Its mostly used for looking at fluorescence, indicative of various things (chemical status, cell shape, watching cells move, location of labeled molecules in cells, ...)
The intensity of the light can also be used to affect living things and chemical things (usually by destroying things, sometimes by making a molecule active by breaking a specific bond).
In addition, there are multiphoton confocal microscopes. These are like a confocals, but rely on a great density of photons (in space and time) to have two (or more) photons arrive at a molecule at the same time (using nanosecond pulse lasers). If they are "there" at the "same time", then their energies can add up (approximately adding) to enough energy to activate the target molecule to fluoresce (or whatever else it might do). Among other things, this gives a greatly enhanced 3D resolution.
As the laser is focused down (along the z-axis) to a very small area (defined by the optics), the photon density goes way up.
The reason this is better than a normal confocal microscope is that the low end limitation on the background of a single photon confocal is the activation by single photons in less focused z-levels (in front of or behind the layer focused on). This kind of activaion in a two photon system is very unlikely due to the requirement of two photons simultaneously for activation.