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2.2.4 Setup of the Vmarker sensor in a “rear projection” configuration
With rear-projection, the projector is positioned behind the screen. The projected image is
visible through the screen. In such an arrangement the Vmarker sensor can also be
positioned behind the screen.
This is because the IR light from the IR pen, like the light from the projection, also shines
through the screen.
The disadvantage of such an arrangement is that you need extra space behind the screen.
This may be reduced by using mirrors, etc.
2.2.5 Other setups
Basically, the Vmarker sensor works almost from any angle. You have to ensure that the
projected image is within range of the Vmarker sensor.
The use of extreme angle is possible but is strongly depending on the projection surface
that is used. Also the angle of the IR-pen to the surface will have a greater influence.
In such case one can change a few settings of the Vmarker sensor to optimize to this
situation.
When using extreme angles also take into account that the accuracy will be reduced.
Ideally, you should try to use the entire range of the sensor that has a ratio of 1:1. You can
see the usage of the sensor after calibration on the Calibration page in the VmarkerUtility.
2.2.6 About the projection surface
It is possible to use the Vmarker sensor on many different projection surfaces. Every
surface that reflects the IR-light of the IR-pen can be used. But of course some are better
then other.
Contrary to what one would expect, highly reflective surfaces are not the best choice. A
matte white surface is basically better than a glossy white surface. The reflection on a
glossy surface is very high and the angle of the IR pen to the surface is more important. A
wrong angle of the IR-pen is missed by the Vmarker sensor. Therefore, a more matte
surface, in which case the reflection is diffuse, is better. The angle of the pen to the plane
becomes less important.
One of the best surfaces to use for your IWB would be a wall, simply painted in
white.
2.2.7 Environment
The Vmarker sensor responds to infrared light. Avoid any other source of infra-red light in
the range of the Vmarker sensor. The largest source of infra-red light is the sun. Direct
sunlight or reflection of sunlight directly into the Vmarker sensor or on the projected image,
will affect correct functioning of the Vmarker sensor. It is even possible that the mouse-
cursor moves seemingly randomly.
Other sources of far infra-red light in their spectrum can also be disruptive. In such case,
much depends on the situation.
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Vmarker Interactive Whiteboard
