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Laser Height Gauge Answered

Hello, I wanted to know if there was a way to build a laser height (measurement) gauge that can measure to .001 or .0001?

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Lets put it this way. Light travels 300000000000 MM in a second.

Your measuring some distance between 0.00254 mm and 127 mm disregard the accuracy for the moment.
The time to travel 0.0254 mm is 8.466666666666667e-15 seconds. You have to design electronics ro handle this.

Usually The phase of the outgoing pulse is compared with the phase of the incoming reflection. the phase difference represents the distance. At least that's how it is done in radar systems - But not to your accuracy.

Although the task isn't impossible, such instruments exist, but it is way beyond DIY unless your skill level is very high. This is why such instruments are very expensive.
You will be better off making manual measurements with a microscope to get the resolution.

Actually, at this scale, laser triangulation works well on the right target, but its not a low cost technology.

Under some circumstances, the OP might be able to use interferometry.

Yes, its possible, but over what distance ?

I feel this is one of those questions where you may not have the skill set to make it work, (mainly because you asked the question).
This is frighteningly small tolerance if accuracy is critical.

You will be comparing the wave front of the outgoing and return laser beam - not easy.

You probably can, but you have to look into the speed and accuracy of your measuring device and sensor. Most likely you have to pulse the laser and determine when the laser light bounces back.