1. Field of the Invention
This invention relates to an optical card handling system used with a general-purpose operating system and a method of accessing an optical card.
2. Description of the Related Art
Information processing techniques have recently been making remarkable progress, and means for recording an increasingly large volume of information have been required. In this connection, what is now attracting attention is an optical information recording/reproducing apparatus.
This type of apparatus uses a recording medium which information can be optically written into and read from. As one of optical information recording/reproducing apparatuses of this type, an optical card apparatus using an optical card as a recording medium has been put to practical use. The optical card apparatus is capable of recording information on an optical card and reproducing the recorded information.
The optical card contains an information recording layer which has the property of changing irreversibly in the presence of heat. By projecting the laser light gathered by a lens onto the information recording layer, pits (holes) can be made in the layer. In this way, the presence and absence of pits (holes) made in the information recording layer represent a data string. Thus, by controlling the formation of pits according to the contents of data to be recorded, the desired data can be written. The reproduction of data is effected by optically sensing the presence and absence of pits in the information recording layer and converting into data.
The optical card has a recording capacity thousands to tens of thousands of times that of a conventional magnetic card. Once data is recorded in an area, the data cannot be rewritten. However, the data capacity that can be recorded on a single optical card is as large as 2 Mbyte to 4 Mbyte. Therefore, the optical card is considered to applied to a variety of uses including bankbooks, pocket maps, and prepaid cards used in shopping. Furthermore, by making use of the advantage that data cannot be rewritten, the optical card is considered to be applied to the case where data must not be falsified.
An example of the optical card is shown in FIG. 12. The optical card 1 shown in the figure is of the credit card size and has a data recording section 2 on its one side. The data recording section 2 is divided into a lot of tracks 2a as the magnetic recording medium is. Each track 2a is straight. Data is recorded sequentially track by track in the direction in which the track extends. The specific areas at both ends of each track 2a, that is, the specific regions at the begin and terminate ends of each track 2a, are used as ID sections 3a, 3b in which information items such as track addresses are recorded.
As described above, the optical card 1 is a medium on which data is recorded in the form of the presence and absence of pits, more specifically, on which data is recorded by forming pits in each track. Once pits are formed, they cannot be filled in, so that new data cannot be written over the track in which data is already written. This type of optical card is called a write-once, read-many type.
However, data can be written in an unused track. Because each track has the ID sections 3a, 3b, a file can be updated as follows. When the data is updated, the whole file including the data items to be updated is recorded on an unused track, and the old data file is discarded. As with the magnetic disk, some tracks are used for file management. Once the file is updated, new file management information is written on unused ones among the file management tracks, and management is effected so that the updated file can be distinguished from the discarded file.
To record and reproduce data onto and from the optical card 1, a read/write beam of laser light must be swept track by track. The light beam may be swept along the track. In addition, the same result may be produced by placing the light beam at a constant position and causing the optical card to move repeatedly along the track.
In general, the optical card is moved along the track and the light source of the optical beam is moved across the track so that data can be read from and written into the desired track.
A detailed structure of the data recording section 2 will be described. As shown in FIG. 13, a plurality of track guides 2a1 are provided at regular intervals in parallel with the track so that each track 2a2 may be formed between two adjacent track guides. Each track guide 2a1 can be sensed optically. A sensor for sensing the track guides is provided. Each track guide is sensed by the sensor. Because each track guide 2a1 and each track 2a2 are arranged along the same lane, the position of the light beam can be controlled so as not to depart from the track lane by sensing the track guide corresponding to the desired track with the sensor and controlling the position of the data read/write light beam so that the beam may move along the track guide. Of course, the data read/write light beam is positioned in the center of the track lane.
In this way, data pits 2a3 representing the recording information can be formed and read along the track 2a2. The track 2a2 of the data recording section 2 (not shown) is further divided into sectors. Data is read and written in sectors.
The data recording section 2 which data is read from and written into has a data area 2b1, a directory storage area 2b2, a change area 2b3, and a change information area 2b4. Namely, some of the tracks in the data recording section 2 are allocated to the data area 2b1, directory storage area 2b2, change area 2b3, and change information area 2b4, which are used as dedicated areas.
The change area 2b3 is an area used for changing the data when a recording error has occurred due to a defective track on the optical card 1, or for logically rewriting the data. The change information area 2b4 is an area in which the fact that the data is written in the change area 2b3 for replacement is recorded.
The data area 2b1 is an area in which the contents of the data forming a file is recorded. The directory storage area 2b2 is an area in which file management information is stored. In the directory storage area 2b2, the necessary information for file management, including a file name, the locations in which the file is recorded, and the length of the file, is recorded. Therefore, by searching the directory storage area 2b2 for the data storage location, the contents of the data can be retrieved.
With the optical card, the reading and writing of information is effected by an optical head composed of an optical system as shown in FIG. 15.
In the optical head shown in FIG. 15, the laser light emitted from a light-emitting element 4 is shaped by a collimate lens into parallel light and then passes through an object lens 6. The object lens 6 focuses the light onto the optical card 1. The reflected light from the optical card 1 passes through a mirror 7, an image forming lens 8, and a beam splitter 9, and is supplied to a detector 10. The detector 10 senses the reflected light and converts it into an electric light.
The detector 10 produces an electric signal according to the presence and absence of pits in the track. Thus, moving the optical card 1 along the track lane enables the data pits 2a3 shown in FIG. 13 to be sensed by the detector 10 in the form of the strength and weakness of the electric signal. Furthermore, in the optical head, the light obtained from the beam splitter 9 is supplied to a focus sensor 11 to sense the deviation of focus. By actuating an object lens driving section 12 according to the sense result of the focus deviation, the position of the object lens 6 is adjusted and thereby the focus is adjusted. To reciprocate the optical card 1 in its longitudinal direction (along the track lane), an optical card driving section 13 is provided. Explanation of a tracking error signal sensing system will be omitted.
When the optical card 1 is used in a computer system, attention should be given to the following points. In the computer system, to use the optical card 1, an optical card recording/reproducing apparatus is connected via an interface. The optical card recording/reproducing apparatus is controlled in various ways under the control of the operating system (OS), the basic program for the computer system, and reads and writes data from and onto the optical card 1.
Many personal computer systems and workstations use UNIX (a trademark of AT&T), MS-DOS (a trademark of Microsoft Corporation), Windows (a trademark of Microsoft Corporation), Macintosh-OS (a trademark of Apple Computer, Inc.), and DOS/V (a trademark of IBM corporation) as an operating system (OS). Under the present conditions, these OSes occupy the position of standard OSes in the fields of personal computer systems and workstations.
With these standard OSes, to manage files for an external storage apparatus, various pieces of information on files are stored in the directory, and on the basis of the information in the directory, the reading and writing of files is effected. These standard OSes differ from each other in the format of directory information and are not interchangeable with one another. Therefore, in a computer system using these standard OSes, when the optical card is read and written, access cannot be effected unless the data format in which data is recorded in the directory storage area 2b2 on the optical card coincides with the data format of the directory on the OS side.
That is, once the format of the directory storage area 2b2 on the optical card 1 is determined, operating systems which can access the optical card 1 are limited.
Generally, the optical card 11 is often carried with the user and used in various places. Consequently, he may encounter the case where his card must be read from or written into with an optical card recording/reproducing apparatus of a computer system running on an OS different from the OS used in recording the data on the optical card.