Patent ID: 8817243

Claim:
An apparatus comprising: a processor; a display coupled to the processor and displaying information to a user of the apparatus; at least a first optical sensor making a series of first measurements, wherein data based on the first measurements are coupled to the processor; at least a second optical sensor making a second measurement, wherein data based on the second measurement are coupled to the processor; and a source of illumination emitting illumination external to the apparatus through a protective barrier; wherein the first optical sensor receives illumination from the source of illumination from external to the apparatus through the protective barrier; wherein based on the series of first measurements the processor determines a peak intensity when the apparatus is a predetermined distance from an object wherein as the apparatus moves towards the object an intensity of illumination received by the first optical sensor increases to the peak intensity at the predetermined distance and as the apparatus moves closer to the object than the predetermined distance the intensity of illumination received by the first optical sensor decreases to less than the peak intensity; wherein the protective barrier has a thickness, wherein the thickness of the protective barrier is less than the predetermined distance; wherein data based on the series of first measurements made with the first optical sensor determines a position of the apparatus with respect to the object.