On an inner wall of a side wall portion of a funnel, a pair of protrusions are integrally formed as glass buildups at positions separated by a predetermined distance from an anode button toward a side of a neck tube. The optical layer can have an optical layer composition different from the substrate composition. A differential pressure sensor detects a pressure difference between both ends of the restrictor. The ROI classifier analyzes objects in an image to arrive at actual features of the true object. Vibration, flexure, and expansioncontraction of the cabinet are damped by shearing forces applied to the damping layer as the rigid layers move in opposite, parallel directions. At least two induction heating coils are provided at selected locations proximate to the melting vessel.