Certain embodiments provide an ultrasound transducer stack. The inventive method for reutilizing plastic receptacles consists in cutting said receptacles into hole-type elements in the form of small tubes and cylinders in order to use them afterwards as heat-shrinkable elements for coating andor connecting construction elements by heat shrinkage while producing elongated articles which are used mainly as construction andor advertising elements. The frame includes a horizontal passage linking the left and right panels and the cable guides. Further, the HMD may be configured to generate a composite image that combines the generated first image and the captured second image. Deterioration of the electron-emitting device due to collision of charged particles is suppressed by the asymmetrical electron-emitting region, electron-emitting efficiency is improved, and a long life is realized.