distance measurment converted to electrical current

Hi. I am trying to find a simple way of measuring distance (hands free) eg with an ultrasonic device and converting the distance reading into a voltage. In other words what i need is to build a system that allows me to create a gradient increase or decrease in Voltage as the object moves further or nearer. The range needs to be no more then 10 meters but it must be able to react to change very quickly or be used to scan an area and get a kind of Voltage "map" of the area based on proximity of objects within that area.

I need to know what components i need and if they can all be bought off the shelf.

I would really appreciate any help or advice on this as i am relatively new to the wonderful world of electronics.

Thanks for reading.