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Accuracy &


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Accuracy &




Accuracy &


A big advantage of the HOLOS sphere approach is that the pen tip can be detected in mid air in 3D anywhere in the field of view of the camera and that also the 3D orientation of the pen is detected. This means the pen can essentially be used like an advanced 3D games controller allowing pointing, gesture recognition and even “drawing” in 3D space. Note that the coordinate values are detected as absolutes in a fixed reference frame, unlike the relative values given by accelerometer/gravitometers in other hand held devices. This means a much higher precision for absolute position and orientation detection can be achieved.

The maximal detection distance from the camera depends both on the Angle of View (AOV) of the camera and the resolution of the camera chip, see some typical examples in Table 2. For a normal lens the active detection volume has the shape of a tipped-over pyramid or “Frustum”, with the pyramid's tip located at the camera’s lens as for example in this setup.

Camera chip



Angle of View

Maximal detection distance

From camera

Detection frustum width and height at maximal distance

VGA, 640 x 480


1.65 m

2 m x 1.5 m

VGA, 640 x 480


2.3 m

2 m x 1.5 m

VGA, 640 x 480


4 m

2 m x 1.5 m

HD720, 1280 x 720


8 m

4 m x 2.2 m

HD1080, 1920 x 1080


12 m

6 m x 3.3 m

For ultra wide angle fish-eye lenses the active volume becomes hemispherical with the camera at the centre and the limit distance being the radius of the hemisphere. For example in our current fish-eye lens setup where we use a 3MP camera and an approximately 180 degree Angle of View, the limit radius is about 2 meters in each direction. Note that these limits only apply for full position and orientation detection and in the case where 3D position alone is sufficient, like for example when the user is a person in the audience (pen held like a games controller), the detection reaches twice as far again.

Figure 6 shows the detection noise on the orientation angle of the pen in 3D in mid air, which ranges from less than 0.07° to 0.33° at 100% of the maximal detection distance  from the camera.

Figure 7 shows the 3 sigma detection noise for the 3D pen tip detection in mid-air. Note that this is the raw detection noise without temporal averaging or smoothing. The accuracy here is not as high as the sub millimeter accuracy achieved in the 2d surface detection case (see Table 1), but still remarkable, for example less than 2 millimeters for up to 2 meters distance at VGA and 3 meters distance at 720HD resolution. In live demo situations users have found our pen to give a much higher feeling of precision for 3D control than typical computer 3D games controllers currently on the market - so accurate in fact that we had first times users draw bicycles in mid-air at demos/presentations. Note also that we are currently developing a stereo camera version of the system where 3D  detection accuracy is improved by a factor 10 to possibly 100.

Table 2

Figure 6

for a full distance, log scale version of this graph click here


Figure 7