Browse Prior Art Database

Photochromic Disk File

IP.com Disclosure Number: IPCOM000075521D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Kazan, B: AUTHOR

Abstract

The arrangement shown in Fig. 1 retains the advantages of self-tracking inherent in grooved plastic disk recording schemes, yet at the same time allows for reading, erasing recording of new information, thus providing a reusable medium. As shown, an optical system is employed for recording information, rather than a mechanical system. To achieve this end, a rotating disk 1 of transparent material is employed, the disk having photochromic material at the bottom of surface grooves, shown at 3. A stylus 5 is arranged to accommodate an optical fiber or light pipe 7, the stylus being fixed to a plate 9 which slides along arm 11. With the stylus riding in the grooves, light as shown at 13 from a laser or other optical source, not shown, can be concentrated as a fine spot at the bottom of the grooves.

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Photochromic Disk File

The arrangement shown in Fig. 1 retains the advantages of self-tracking inherent in grooved plastic disk recording schemes, yet at the same time allows for reading, erasing recording of new information, thus providing a reusable medium. As shown, an optical system is employed for recording information, rather than a mechanical system. To achieve this end, a rotating disk 1 of transparent material is employed, the disk having photochromic material at the bottom of surface grooves, shown at 3. A stylus 5 is arranged to accommodate an optical fiber or light pipe 7, the stylus being fixed to a plate 9 which slides along arm 11. With the stylus riding in the grooves, light as shown at 13 from a laser or other optical source, not shown, can be concentrated as a fine spot at the bottom of the grooves. By modulating the intensity of the light as the disk is rotated, periodic variations in the darkening of the photochromic material can be produced. The information recorded can be read out by transmitting light through a fiber, of a much lower intensity and of a wavelength which falls within the induced absorption band of the material. The transmitted light is monitored by photocell 15, positioned below the stylus on the opposite side of the disk. For erasing, a higher level of suitable long wavelength light may be transmitted through the fiber, causing bleaching of the photochromic material.

Fig. 2 shows an alternative technique for intercepting the laser light and guiding it into grooves in the disk. Here the stylus consists of a flat sapphire platelet tapered to a narrow neck, as shown at 17. On the opposite edges of the tapered sapphire, additional sapphire segments 19 and 21 are cemented by a material having a lower index of refraction. As shown, parallel light from the laser source is reflected from mirror 23, attached to the stylus and reflected onto the surface of the sapphire, at the appropriate angle. Utilizing a grating of insulating material on the surface, shown at 25, the incident light is transferred into the sapphire plate and, then guided into the lower constricted portion which rides in the grooves of the disk. Although not shown, it is recognized that light of different wavelengths from more than one laser can be directed onto the optical system, thus allowing rapid switching into the modes of writing, reading or erasing, by electronically switching on the appropriate laser. For continuous...