Abstract: Systems and methods for optically imaging a dental structure within an oral cavity by moving one or more image apertures on an arm coupled to a fixed coordinate reference frame external to the oral cavity; determining the position of the one or more image apertures using the fixed external coordinate reference frame; capturing one or more images of the dental structure through one or more of the image apertures; and generating a 3D model of the dental structure based on the captured images.

Abstract: A magnetic tape cartridge has a thin cartridge casing having flat upper and lower surfaces and a single reel around which a magnetic tape is wound. Projections are provided on at least three places of the lower surfaces of the cartridge casing near the leading edge and the trailing edge of the cartridge casing and recesses, which can engage with the projections, are provided on the upper surface of the cartridge casing so that, when a plurality of the magnetic tape cartridges are stacked, the projections and the recesses of the cartridge casings of magnetic tape cartridges are engaged with each other, whereby the magnetic tape cartridges are prevented from being displaced with respect to each other when they are stacked and the sliding resistance when the magnetic tape cartridge is inserted into a recording and reproducing apparatus is reduced.