Camera Phones with Pen Input as Annotation Devices 

Michael Rohs and Christof Roduner Institute for Pervasive Computing, ETH 
Zurich 

This paper explores the use of camera phones with pen input as a platform for 
generating digital annotations to realworld objects. We analyze the 
client-side requirements for a general annotation system that is applicable in 
mobile as well as stationary settings. We outline ways to create and interact 
with digital annotations using the camera and pen-based input. Two 
prototypically implemented annotation techniques are presented. The first 
technique uses visual markers for digital annotations of individual items in 
printed photos. The second technique addresses the annotation of street signs 
and indication panels. It is based on image matching supported by 
interactively established 4-point correspondences.