Proximity sensor with varying levels

I am starting a project and would be grateful for any hints.

I need something similar to the common IR LED and phototransistor proximity sensor. These measure the reflected light from an object and switch on at a certain point. They have a pulsed signal to avoid false triggering by ambient light. What I require, though, is a rough measure of the amount of reflected light rather than just on/off. 3 or 4 bits precision would be ok. All the circuits I have been able to find just switch on and off and don't offer a varying level.

Secondly, I need 10 channels of the above so I'd like to have as few components as possible duplicated 10 times!

It would like to use an Arduino to process the input from these sensors so am looking for something easy to interface.

Any ideas gratefully received. Pointers to circuits or chips or suggestions for alternative approaches would all be great. Thanks in advance.

Julian

If you use the analog pins on the arduino and some 4051 ic you might achive this... Have a look at http://natebu.wordpress.com/ really cool project that uses ir diods and phototransistor to detect objects... They also use arduino btw...

/Jon