Interactive display apparatus and method for operating the same

An interactive display apparatus, comprising

• a projector for projecting, from an origin, an image defined by image data onto a projection surface;
• a sensing device for 3D sensing in a monitored space between the origin and the projection surface and for generating 3D sensing data representative of results of the 3D sensing;
• and
• a control unit operationally connected to the projector and to the sensing device, which is configured for
• computing from initial 3D sensing data generated in a calibration phase by the sensing device, reference surface data representative of a virtual reference surface corresponding to the projection surface;
• controlling the sensing device to generate, in an operational phase which is subsequent to the calibration phase and in which an object is located in the monitored space, secondary 3D sensing data;
• retrieving a measurement offset value;
• determining from the secondary 3D sensing data and the reference surface data, a measured height representative of a sum of the measurement offset value and a distance between the object and the projection surface;
• and
• generating a trigger signal if the measured height minus the measurement offset value amounts to a positive non-zero trigger distance or to less than the trigger distance.