Wiper System measures the pressure distribution between the wiper blade and the windshield. The homogeneous force profile leads to perfect visibility. Uneven profile can cause scratches.
In the event of too low a force due to poor contact or bulging of the pen, the wiper leaves a dirty glass. Many car windshields are built of complex curvatures, which is quite a challenge for windshield wipers. The pen can fit well in one position, but not in the other.
Results of force measurements - pióro wycieraczki pod kątem 30° do szyby