BINARY INFORMATION STORAGE

摘要

1486271 Data store INTERNATIONAL BUSINESS MACHINES CORP 21 March 1974 [30 March 1973] 12735/74 Heading G4C Binary data is stored, retrieved, and erased using a storage material which, at least at its surface exists in semiconductor and metal phases, the data being stored by inducing a metal to semiconductor phase transition by reducing the internal stress in the material at the desired location below a first threshold value, the data being retrieved by optically distinguishing between the two phases, and the data being erased either in bulk or at selected locations by inducing a semiconductor to metal phase transition by subjecting the material to an internal stress above a second threshold value greater than the first threshold value. The storage material may be samarium sulphide and reading, writing, and erasing is performed using a laser. Figs. 1-6 (not shown) illustrate schematic embodiments in which, e.g. the storage material is bent so as mechanically to stress the material to a point intermediate the two thresholds. Data is then written, read, and erased by the selective use of two lasers, one of high power and one of low power, the high power laser being used to stress the storage material above the second threshold to erase data and the low power laser being used to read data and to reduce the stress below the first, low, threshold to write data. Alternatively erasure may be performed by polishing or bending the material. Two practical embodiments are described. In the first, Fig. 7, a stationary disc 23 of storage material is used in conjunction with a beam deflector 25 to selectively access desired locations on the disc using beams from a read/write laser 31 and an erase laser 33. In the second Fig. 9 (not shown) a rotating disc is used together with a radially movable head incorporating the lasers. In the latter case each data track on the disc includes two adjacent tracks, one for the stored data and the other on which the erase beam is directed to erase data from the adjacent data track. It is also stated that ultrasonic vibrations may be used to erase selected locations in the storage material.