Capacitive proximity sensor size?
The range is directly related to the size of the sensor.  The bigger the sensor, the bigger the range.

We've been making capacitive sensors at work, directly on PCBs.  In my experience, you can sense presence at a distance of 75% of the sensor diameter.  So if you want to sense presence at 10cm to 15cm, I'd start with a sensor diameter of at least 20cm.   


  The range in which a probe is useful is a function of the size of the sensing area. The greater the area, the larger the range. The driver electronics are designed for a certain amount of capacitance at the probe. Therefore, a smaller probe must be considerably closer to the target to achieve the desired amount of capacitance. The electronics are adjustable during calibration but there is a limit to the range of adjustment.
  In general, the maximum gap at which a probe is useful is approximately 40% of the sensing area diameter. Standard calibrations usually keep the gap considerably less than that. 


http://www.lionprecision.com/tech-library/technotes/cap-0020-sensor-theory.html