What sensor should I use to sense the distance of an unknown object?
I'm trying to put together a project for the first time with an arduino uno board.
The aim of my project is to sense the distance/position/proximity of ANY object away from my sensor (board). Ideally, I want a system that is able to give good reading if the system is operating out-doors. The entire system is housed inside a box with only the power line coming out of it. The cost of the system should be cheap enough for a small, hobby project. The range of the sensor should be about 2cm to 3m.
I've looked at IR, ultrasound, and hall-effect sensors. They're not really what I need because
1. IR sensor doesn't work well out-doors
2. Ultrasound sensor has to be exposed outside of a container to send out the sound waves.
3. Hall-effect sensor needs the object being detected to have a magnet attached to it.
So are there other options I can go with?? A different kind of magnetic sensor where if the magnetic field it produced was disrupted by an unknown object, the sensor can give me back a distance reading of that object?