A typical computer mouse has the sensor elevated at just the right height. For the ADNS-9800, this is approximately, this is approximately 2.4mm. HOWEVER this is not a concern for our application as we aren't detecting the small particles of the surface. Instead, it's important to position the sensor at exactly the right distance so that individual letters are captured on the camera. As a result, the "pen" may look less like a normal "pen" but instead a tubular device that needs to be in contact with the paper.