i can't speak english very well...
The best way to measure distance is to use a sharp sensor (infrared) or ultrasonic ranger.
i think what you mean with normal infrared sensors is a ir emitting diode and a photocell but with that equipment you can't measure a distance!
but the sharp gp2d12 for example is an infrared distance sensor which goes from 10 to 80 cm with an analog output.
you can directly connect the sensor to an analogport of the c-control
cost: 10€ - 20€ i think
the srf-08 is an ultrasonic ranger with a range of 3 cm - 6m and it uses the I²C bus protocol to communicate with the ccrp5 for example...
but it costs: 25€ - 40€
i prefer the gp2d12
i hope you can understand my english