Mechanical Ghost Palpation (MGP): Application of Ghost Imaging for Tactile Sensing and Basic Validation

To achieve global palpation efficiently and without the use of tactile sensors, this study proposes mechanical ghost palpation (MGP), which applies the concept of ghost imaging (GI) to palpation, and verifies its basic principle. However, unlike general GI, which uses light as a medium, the configuration of the pressing patterns in MGP, which involves mechanical contact, presents system-specific challenges: from the correlation between the pattern structure and pressing depth, to the replacement and mass production of the patterns. To overcome these issues, in this work, we proposed a pattern configuration method that imposes constraints on the number of contact points and the centroid of their positions, and further proposed a technique to virtually increase pattern diversity by using a rotation operation on two square patterns. In the experiment, we estimated the stiffness map of a silicone gel phantom containing an embedded inclusion within a 5×5 grid by performing a total of 8 times pressing operations (using two pressing patterns). The results confirmed that the inclusion’s location was included within the top three highest-stiffness positions in the MGP-estimated stiffness map. This achievement demonstrates the potential of MGP to efficiently perform global palpation independent of tactile sensors.