Importance

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Abstract

A digital pen is provided with an optical system with at least one sensor for capturing images of a patterned surface and at least one light source for illuminating the patterned surface when images are captured by the at least one sensor. In order to solve the problem that the sensor is sometimes blinded by specularly reflected light when the digital pen is used on a glossy surface, the optical system is adjustable between at least two image capturing states in which images are captured with a different geometrical arrangement of the at least one sensor and the at least one light source. As a supplement or alternative, the digital pen may illuminate the patterned surface with linearly polarized light having a first polarization direction and further be provided with a linear polarizer in front of the image sensor, which polarizer has a second different polarization direction, preventing specularly reflected light from reaching the sensor.

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First Claim