  In this paper, we present the TacShade a newly designed 3D-printed soft
optical tactile sensor. The sensor is developed for shape reconstruction under
the inspiration of sketch drawing that uses the density of sketch lines to draw
light and shadow, resulting in the creation of a 3D-view effect. TacShade,
building upon the strengths of the TacTip, a single-camera tactile sensor of
large in-depth deformation and being sensitive to edge and surface following,
improves the structure in that the markers are distributed within the gap of
papillae pins. Variations in light, dark, and grey effects can be generated
inside the sensor through external contact interactions. The contours of the
contacting objects are outlined by white markers, while the contact depth
characteristics can be indirectly obtained from the distribution of black pins
and white markers, creating a 2.5D visualization. Based on the imaging effect,
we improve the Shape from Shading (SFS) algorithm to process tactile images,
enabling a coarse but fast reconstruction for the contact objects. Two
experiments are performed. The first verifies TacShade s ability to reconstruct
the shape of the contact objects through one image for object distinction. The
second experiment shows the shape reconstruction capability of TacShade for a
large panel with ridged patterns based on the location of robots and image
splicing technology.
