For the optical inspection of products (10) with the aid of electronic image processing, height-dependent shape characteristics of the products are derived from a height image signal supplied by an imaging triangulation system (20) in addition to quality features derived by an image processing system (15) from the image signal supplied by an inspection camera (12). In order to obtain said height image signal quickly and easily, a light edge (23) is projected on the products (10) transversely to their direction of movement and imaged by a triangulation line camera (21) at an angle to the direction of projection. The light edge is opticaly imaged on the sensor components of the triangulation line camera in such a way that the image of the light edge (25) lies on the sensor components (32) over the entire height range of the products and a proportion of each sensor component, dependent on the local product height, is illuminated by the light plane (26) bounded by the light edge. The analog output signals from the sensor components then directly provide a height image signal from which the required height-dependent shape characteristics may be derived.