measuring small distances (< 40 cm) with large precision

Dear All, I need to make a device to measure small distances with great precision (< 1mm). I take a look in the ultrasonic sensor, but its precision is around 3 mm, quite large for my need. Thus, i was wondering in using laser instead ultrasonic. does anyone have an idea in how can i do that?

Thanks!

Leo

Have you seen these? It's not clear what resolution you can expect, you might get 1mm, but not sub-mm.

It might be possible to improve accuracy of an US sensor by measuring the time of flight with a faster clock frequency and/or measure phase shift to get better accuracy.

Laser time of flight sensors like the one referenced above might be able to do it. Laser interferometry can easily do it, but is expensive. I would take a look at some of the LIDAR systems to see what they can do.

If you can use a contact sensor there are a lot of options. There are some online guides to hacking a cheap digital caliper. Linear Variable Differential Transformers (LVDT) can easily get that level of accuracy.