how can i build a Thickness meter with Micrometer accuracy?

[Delphianrex]

hi dear friends,
I'm about to build a Thickness meter with the precision of Micrometer.
I was wondering if using ultrasonic or laser. ultrasonic is capable of doing it or not?

putting any sample code using AVR MCU would be appreciated.
Please fully explain your claims.

Thanks in advance

 

[horace1]

I would think either a laser or an ultrasonic device would be worth looking at.
Have a look at commercial organisations that produce such devices and see what they use, e.g.
**broken link removed**

it may give you some ideas