Diminished reality as challenging extension of mixed and augmented reality

Diminished Reality (DR) has been considered as a sub-technology of Mixed and Augmented Reality (AR/MR). While AR/MR means technologies that add and/or overlay visual information onto images of real scene for providing users to enhance their visual experiences with the added/overlaid information, DR aims the similar enhanced visual experiences by deleting visual information from the images of real scene. Adding and deleting visual information might be considered as same technical issues, but they are actually totally different. In DR, visual information that is hidden by the deleted object should be recovered for filling into the deleted area. This recovery of the hidden area is not required for general adding/overlaying based AR/MR, but should be one of the typical issues for achieving DR. Camera pose estimation and tracking is a typical issue in AR/MR, but the condition of the scene and required performance for DR are not always the same as AR/MR. For example, the object to be diminished/removed should be detected and tracked while the camera is freely moving for DR. In this tutorial, challenging technical issues for DR are addressed, such as recovery of hidden area, detecting and tracking the object to be removed/diminished, tracking camera poses, illumination matching and re-lighting, etc. In addition to those technical issues for DR, a survey of applications of DR, expected futures with DR, and human factors of DR are also presented.