Optical tape position sensing system for magnetic tape media in computer

Abstract

A computer memory backup device which utilizes magnetic tape media having aperture indications at the beginning-of-tape (bot) and the end-of-tape (eot) for accomplishing the sensing of the same is disclosed. The present invention utilizes a light pipe for directing the emitted electromagnetic radiation from an isolated source to the magnetic tape media, and focuses the radiation in proximity to the media. An integral focusing lens disposed on the exit end of the light pipe serves to converge the exiting electromagnetic radiation in this fashion. The electromagnetic radiation source, shown as a light emitting diode, is pulsed in a manner such that accuracy, as well as energy conservation, is greatly increased. A time domain filtering method is employed as a means to further enhance the system's accuracy in sensing the beginning-of-tape and end-of-tape. The devices accommodate standard aperture indications as required by ANSI specifications in both dimensional and placement aspects. When these aperture indications reach the area at which the electromagnetic radiation is being focused they permit the electromagnetic radiation to pass through the magnetic tape media at which point the electromagnetic radiation is sensed. A determination is then made appropriately as to either the beginning-of-tape or end-of-tape.