Electronic – Short Distance sensitive laser range finder


I am looking for a reference design for a laser range estimator. I actually don't want to measure the absolute distance but the relative position of the object that is interest. i.e. if it is getting closer or not.

The range of the object is between 50 to 20 cm and object has a movement of a few millimeters and i like to measure this movement using laser. Ultrasound is not an option due to the speed of the object.

Any ideas or pointers?

Thx, Frank.

Best Answer

Your task screams "Please, use interferometer" here :-) Basically, you measure phase difference between laser itself & reflected beam through interference.

This way you may get precision down to 0.1 micron, but you should be ready to count all these 10'000 phase changes per second (I.e. if you skip one - you've got 0.7 micron error).

Speed of tracked object is virtually unlimited.

But this is not going to be weekend project :-)