Re: laser control circuits

Howhurley wrote:
Hello,

I am looking for laser control circuits to use as distance measuring
applications. A set frequency output with a detector circuit might do
the trick. Any suggestions?


The difficulty of laser ranging problems can range from easy (across your living room with the lights turned off) to difficult (hitting the lunar corner reflector left by Apollo 11) to impossible (using a battery powered handheld unit to measure 500 yards distance to a shiny target in bright sunlight).

The difficulty generally comes from not having enough signal to overcome the noise of the background light. So first you need to do a back-of-the-envelope photon budget, to see if you have enough light for the job, and if not, how you can get more. If you don't know how to do this, I'll walk you through it if you post the following information:

1. How far are you trying to go?

2. What's the ambient light level? (Interstellar space? Living room? Bright sunlight? The interior of an arc lamp?) (None of these is necessarily impossible, and all have been done.)

3. What are you trying to hit? (Retroreflective tape? A white wall? Dirt? Raindrops? A bad guy dressed in black hiding behind a bush?)

Photon budgets are pretty easy once you've done a few, and they're very rewarding, because they actually give the right answer. A decent design will almost always be withing 3 dB of the budget, and usually it'll be within 1 dB. Seeing that happen is some of the best fun I know.

Cheers,

Phil Hobbs
.