3-Click

Finding the display: the 3-click setup

When the Upoint remote is equipped with a (cheap) ultrasonic distance sensor the setup procedure consists of pointing to three characteristic points on the display: the lower-right corner, the upper-right corner and the point closest to the user. All three points are indicated by the system, and the user merely needs to highlight them (approximately) when asked to do so.

Using an ultrasonic distance sensor: the 3-click setup procedure

Internally, the Upoint software measures the orientation of the pointing lines during the first two measurements. Using the assumptions mentioned in the section on finding the display (i.e., it has vertical and horizontal edges), this constitutes enough information to find its orientation and, consequently, the direction of the point lying closest to the user. The third measurement then measures the shortest distance between the user and the display and, assuming the aspect ratio is known with sufficient accuracy, allowing the display's size to be uniquely established.

This procedure does, obviously, somewhat constrain the user's position from which the setup is to be performed. That is, the position of the user relative to the display must be such that the physical vertical plane in which the display approximately lies (e.g., the wall on which the screen is mounted) needs to contain the point of the infinitely extended version of that plane that is closest to the user. This is of course a bit theoretical; suffice to say that for most practical situations it's best if the user positions him or herself in front of the display during this one-time setup procedure.

The 3-click setup procedure: components used