There is described a closable opening device for a sealed package containing a pourable food product. This invention makes it possible to determine with a high accuracy whether an area to be determined is a character area. A satellite includes a transceiver for transmitting and receiving the optical communications signal and includes adaptive optics for determining the shape of any distortions in the waveform of the optical communications signal and compensating at the satellite for the distortions. The chipping tools have at least one bore, formed perpendicular to the division line, the bore extends across the utilization area and ends at the division line between the core area and the utilization area. A region irradiated with the electron beam emitted from the electron-emitting device is not larger than the phosphor dot, a part of the black member is disposed in the region irradiated with the electron beam, and at least a part of the aperture is disposed outside of the region irradiated with the electron beam.