I feel like I've asked this before.
Using a general lens, or a microscope objective, can we focus a laser to a much smaller point, say 5 microns or less? Converging the beam, which then diverges rapidly after the smallest point is fine, I'm not talking about keeping it collimated.
I'd like to take something like a low power green laser, and pass it through a transparency with a sensor on the other side to read in the optical density essentially (how much light the sensor picks up) as it sweeps across, I'd like a small point, for a more detailed reading of course.
So the other restriction is, it shouldn't be powerful enough to burn anything or wreck what I'm reading. Of course I could use ND filters.
Using a general lens, or a microscope objective, can we focus a laser to a much smaller point, say 5 microns or less? Converging the beam, which then diverges rapidly after the smallest point is fine, I'm not talking about keeping it collimated.
I'd like to take something like a low power green laser, and pass it through a transparency with a sensor on the other side to read in the optical density essentially (how much light the sensor picks up) as it sweeps across, I'd like a small point, for a more detailed reading of course.
So the other restriction is, it shouldn't be powerful enough to burn anything or wreck what I'm reading. Of course I could use ND filters.