Abstract: The invention provides a process for checking the bonding of the cellular core of a honeycomb to a skin, said process comprising the steps of: using a light source to illuminate a so-called illuminated zone on the free surface of the honeycomb so as to illuminate the interior of the cells opening out into said illuminated zone, and detecting the emergent light exiting the cells in a so-called observed zone. The minimum distance between said illuminated zone and said observed zone is denoted E and defines a direction D, the distance E being at least equal to the width L1 of the cell mouths measured in the direction D, so as to make it impossible for the illuminated zone and the observed zone to be simultaneously above the mouth of one and the same cell. The invention also provides an instrument for implementing the process.