Browse Prior Art Database

Used Space Evaluation

IP.com Disclosure Number: IPCOM000030911D
Original Publication Date: 2004-Sep-01
Included in the Prior Art Database: 2004-Sep-01
Document File: 3 page(s) / 65K

Publishing Venue

IBM

Abstract

In order to evaluate the free or occupied space in a CD disk, usually there is the need to use a CD drive and computer resources to read the data from the disk in order to evaluate the space. This can be avoided by using a more simple optical device.

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Used Space Evaluation

Disclosed is a system to evaluate the free or occupied space in a CD disk in a more effective and simple way, without involving any PC resource, without using a CD drive and without the need to rotate the disk: It works by using a light beam, a sensor and few logic circuits. It is a very cheap device, using a limited amount of energy and resources.

    Actually when the disk is burned, the full area has a different "color" compared with the empty area. The light reflection of the two areas is different. Linearly moving a beam light from the centre to the edge of the disk, and evaluating the light reflection, when it changes end the full area. By evaluating the position of the light during the scan, the amount of space can be easily evaluated, as follows.

Fig. 1 CD disk

Based on figure 1, the total area available for use (At) is shown in Formula 1:

Formula 1

While the used area (Ax) is shown in Formula 2:

Formula 2

    Assumed that the max size in Mb is a constant for the disk, C (for ex 750 Mb), the used space (U) can be evaluated as shown in Formula 3:

1

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Formula 3

Considering that the difference shown in Formula 4:

Formula 4

is a constant quantity too, defining the constants K and K1 as shown in Formula 5:

Formula 5

    Considering that R1 is a constant value too, the disk used space U can be obtained by simply evaluating Rx as shown in Formula 5 in bytes or in percentage respectivel...