# Laser rangefinder

Hello.

I would like to make a laser rangefinder which could measure up to 10-15 m with accuracy around 1-4 mm. I have looked at various approaches (triangulation, TOF, phase shift) but can't decide which one would be appropriate for my needs and also which one could be realised with hobby electronics.

Any help/ideas would be appreciated.

Best regards, Sašo

Creating a laser rangefinder would be extremely difficult for most hobbyists. However, you can buy one that works well here: http://pulsedlight3d.com/

I have looked at this product. I have also looked at OSLRF-01, which can measure up to 9 m. I have a 50mW laser diode paired with avalanche photodiode with optics. Problem in calculating distance is speed. The description of OSLRF-01 module states, that it “slows down” the speed of light to approx. the speed of sound which is more managable. I’m not quite sure, how this is done. They are writing something about oscilators and comparers. Any thougts anyone?

Thank you.

You can dramatically slow down light under extremely special circumstances in the laboratory, but not in a consumer product.

It would not surprise me if the two devices use similar techniques to sample the reflected pulse, but this is not something an amateur can do, or the market would be flooded with cheap laser rangefinders.

I did not mean that they actually slow down the light. They write something about expanding received signal so it is easier to process. After that they compare phases of sent and received signals and from that the travelled distance is calculated. I understand the process of phase unwrapping, comparing and calculating it to the certain distance without ambiguity, but I can not wrap my mind around the idea how to build working circuit (which components to use and how).

Thanks anyway.

Whatever you do with a laser range finder your problem is the speed of light is incredebly high. In a single nanosecond light travels 30cm. If you really need a resolution of 1-4mm you are talking about a resolution of 25ps or better in the time scale. Or if you want to put it in the frequency scale thats 40GHz or better. Measuring something like this is possible but it is not easy. I just googled for laser range finder prices and you basically see a direct link between increasing resolution and fast increasing prices. If you want to try to do something like that yourself it might be worth to have a look how the short pulse laser community is measuring their laser pulses. They have to deal with the picosecond, femtosecond or even attosecond timescale on a daily basis.

By the way be careful with your 50mW laser diode. It is most definetely powerful enough to harm your eye seriously. You might even be able bo burn your skin. A laser diode like that shouldn't be operated without proper eye protection.

Daniel