NL8900611A - OPTICAL OR MAGNETO-OPTICAL DATA SYSTEM. - Google Patents

Description

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Optical or magneto-optical data system

The invention relates to the field of optical information storage systems.

The current emphasis in the development of information storage systems is the suitability for storing more and more information in a computer memory system with so-called "desk top" dimensions. These "desk top" sized memory systems containing magnetically described hard disk media, such as those used in Windchester disk drive type memory systems, currently have the capacity to store more than 20 megabytes of magnetically recorded information. The problem with such memory systems is that the hard disk medium is necessarily permanently installed in the computer. Since the medium cannot be easily removed, the user is limited to any portion of the hard disk remaining for information storage at the time of use. Thus, information storage systems operating with magnetically described hard disk media are not considered a potential solution for increasing the information storage capacity.

Memory systems with so-called "floppy discs" in which flexible plates each having a diameter of either 5.25 inch or 3.50 inch, are used as the storage medium, provide easily removable storage media. However, the problem with such storage systems is that the current storage capacity of information magnetically recorded on a single floppy disc used in such a system has not yet reached a level equal to that of the hard drive, which that is, a single floppy disc as a medium can only store about 1 to 2 megabytes of magnetically captured information.

Systems for storing information using ¢ 90061 1.

optical access devices have received significant attention due to their potential capacity to store significantly more data, ie on the order of 400 to 800 megabytes of information, than is available in magnetically described at -5 battle systems with either hard drives or floppy discs. One reason for the considerably greater storage capacity of optical storage systems is that the diameter of a focused light beam used for reading or writing information is typically only 1 micron (microns). The information density 10 recorded on a medium is therefore much greater than the density characteristic of a magnetic recording. In addition, the medium for use in such optical systems may have the shape similar to that of a so-called "floppy disc", that is, a medium that can be easily. be removed. Unfortunately, major problems remain in the way of the development and commercial acceptance of such optical systems, namely the relative slowness with which information can be retrieved compared to magnetic storage systems, the current size limitations of so-called desk top computers and the suitability to write or erase information many times and re-write to a single copy of the medium.

First consider the current size limitations. So-called "desk top" computers include a number of modular components, in particular information storage systems, which can be added inside the computer case to provide a degree of buyer compliance to provide a certain need. Since such components can be of various sizes, the American National Standards Institute has adopted certain external dimension standards for such components, which standards are generally referred to as the full-height standard and the half-height standard. Since the half-height standard seems to be the most desirable for such modular components, there is a need to develop an optical information storage system that will fit the half-height standard. The half-height standard for modular components is the following: height 1,625 inches; 35 width 5.75 inches and depth 8.00 inches. The problem with the current optical storage systems is that the existing designs and techniques require components that easily exceed this size standard when assembled together. It appears that only some of the currently available systems are equipped with an optical head which can be used in such an 89006 1 1. *

a

-3- measurement standard would fit, but this is only a single component of an optical storage system.

Now consider the relative slowness with which information can be retrieved in current optical information systems in equation 5 with magnetic storage systems. The main factor contributing to the problem of slow speed of access to the optical storage systems, is the weight of the optical head. It will be appreciated that the greater the weight of an apparatus for reading out or writing on an optical disc, the more difficult and thus slower it will be to orient such an apparatus with respect to precise locations on the rotating disc.

Existing optical storage systems include those found in video recorders or compact discs (CDs) of the type of the read-only type, and the players bearing the name "write once read many times (WORM ) "optical storage systems. Currently, the ability to write and read from an optical disc many times is primarily limited by the media available for use in such a system, although it should be understood that the present invention is not limited to only media that already exist.

In current CD systems, an optical disc is rotated about a central axis. A laser beam is projected onto the surface of the disc by means of a lens, a reflecting mirror or beam splitter, and a projection lens. The laser beam is modulated by the information recorded on the optical disk, and the modulated light is detected by means of a photo detector. Output signals from the photo detector are supplied to a processor for supplying information signals and tracking signals. The source of the laser beam, the lens, the mirror, the projection lens and the detector are collectively referred to as an optical head assembly. The optical head assembly is typically moved radially across the rotating disk to access the information recorded on the disk.

Since the information to be read or written is contained in narrow tracks on an optical disc, coarse and fine radial displacement mechanisms are provided. Until now it has not been possible or even considered desirable to combine coarse and fine displacements in a single mechanism. The coarse radial displacement mechanism typically includes either a pivot arm or 8900611.

* -4- a radially oriented track which moves the optical head assembly in a radial direction over many tracks. The fine radial displacement mechanism generally operates by displacing the projection lens either along a radial axis which causes the projection lens to move between some adjacent tracks, or along an axis generally perpendicular to the disc, thereby projection lens can focus the laser beam dynamically on the surface of the disk while rotating it. Such fine displacement mechanisms can be found in the commercially available optical head assemblies sold by Olympus Corporation, Lake Success, N.Y. (TAOHS series) or by Pentax Teknologies, Broomfield, Col. (VU-108-02 series). An example of such an optical head assembly can also be found in U.S. Patent No. 4092529 - Aihara et al. The height of these fine displacement mechanisms 15 also contributes to the problem of size limitation. reference to the WORM optical storage system described in Rosch, Winn L, "WORM's for Mass Storage" PC Magazine, Volume 6, No. 12 (June 23, 1987), biz. 135-148.

Since the fine displacement mechanism typically causes displacement of the projection lens through the use of relatively massive electromagnets, the total weight of the optical head assembly is such that displacement of the assembly is laborious and thus relatively slow. In an attempt to solve the access time problem, reports of attempts to reduce the optical head assembly have appeared. However, since the fine displacement mechanism is still an essential part, the weight and dimensions contributed by such a mechanism remain. For example, Fukui, Y.et al, describes "New servo method with eccentricity correction circuit" Visual Engineering, Volume 26, no.

30 11 (November 1987), biz. 1140-1145, an optical head assembly that combines an anamorphic prism, a convex lens, and a roof-shaped prism in an attempt to derive data and tracking information signals from a single beam of light. Such a combination has been found to result in fewer optical parts: however, the dimensions and weight of the fine displacement mechanism remain.

Writing information into a disc with the current optical systems is typically accomplished by burning the information into the medium. Currently, no available media has been developed in which such burn-in can be easily erased and 8300611 ^ * -5- re-registered.

A mixture of the optical and magnetic information storage systems, so-called magneto-optical information storage systems, seem to offer the opportunity to fulfill not only the desire for a larger storage capacity but also the need to obliterate optical information and re-enrollment of new optical information. It is estimated that the theoretical upper limit of the storage capacity of such systems can be as much as 300 megabytes per square inch of the medium. However, in practice a registration of about 400 to 800 megabytes can be expected on a 5.25 inch 10 floppy disc.

In magneto-optical storage, data is written and erased on a thin film of magnetic material with properties to be described here. As with a magnetic recording, the information is recorded as a series of bits where the magnetic field of the film at a given point is either north pole up (a digital 1) or north pole down (a digital 0). All magnetic poles of a blank disc are oriented with the north pole pointing downwards. The drawback of the magneto-optical media is that the magnetic field required for turning a magnetic domain from the north pole down to the north pole upwards, ie the coercive field, varies widely with temperature. The room temperature is the coercive field needed to get a North Pole turn, so large that an ordinary magnet is too weak. At about 150 ° C, the coercive force required for domain switching does not drop to substantially zero and a bit can be recorded using known magnetic recording techniques. In a magneto-optical system, optical techniques are used to heat selected spots on the medium that passes close to a relatively large electromagnet. In this way, a point of the medium can be heated, decreasing the coercive field required for writing a bit of information, and the magnet, depending on its own Arctic orientation, can thus record the desired bit. Once the last ray is expanded, the newly heated point in the medium cools, the "frozen north pole" being "frozen" in the desired direction. To erase such recorded information, the process need only be reversed, that is, the point of the medium will be heated by the laser beam and the orientation of the north pole of the magnet will be such as 89 00 61 t / i * -6 - will be that north poles present in the medium will be oriented in a downward direction.

Since it is not desirable to have any contact with the medium, relatively large electromagnets were used. Since such magnets are relatively slow in changing their own pole orientation according to the supplied electrical signal, the poles in the medium are oriented by modulating, for example turning the laser on and off, while the magnetic field remains relatively constant.

The reading of information thus recorded on a magneto-optical disc is only achieved with the aid of optical components. A relatively weak beam of light is focused on the medium. The reflected light is read either above or below the medium. Due to phenomena known as the magneto-optical Curry effect and the Faraday effect, light coming from or passing through the medium will have slightly different polarization than the light focused on the medium. The change in the polarization direction will be either clockwise or counterclockwise depending on the orientation of the north pole at that point. For a more illustrative interpretation of the magneto-optical action described above, reference is made to Freese, Robert P. "Optical disks become erasable", IEEE Spectrum, February 1988, biz.

41-45.

The problem with such magneto-optical information storage systems is the ability to write over information without going twice over the same point of the medium. Until now, the main method of writing over information in a magneto-optical system has been a two-stage process. First, a run was made over the medium to erase all 20 information in a given track. Secondly, a second run was made on the same points to now record the desired information. Since during magneto-optical recording the bearing is switched on and off at a high frequency while the medium continues to move above an electromagnet with a relatively constant magnetic field, the two-stage process was the most important method for ensure that no unwanted information is left on the disk after completion of the overwrite operation.

Attempts to solve this problem involved the use of two optical heads and associated electromagnets apparently placed in a 8900611 * * -7-lead / lag mode, so that the leading head can erase in the same pass over the medium in which information is recorded . A second attempt to solve the two-corridor problem was the proposed use of juxtaposed light beams focused on adjacent tracks.

Yet another proposal for solving this problem was to keep the laser beam energy constant while modulating the magnetic field. The latter Proposal was rejected in Kobori, Hiromichi et al, "New magneto-optic head with a built-in generator for a bias 10 magnetic field", Applied Optics, Volume 27, No. 4 (February 15, 1988), biz. 698-702. The reason given for this rejection was that to obtain high data bit rates, the magnetic field generator (the magnetic head) had to be placed close to the medium. As a result, it would not only be difficult to take a double-sided disc, but also preserve the removability of the disc.

As a result, there is still a need for a magneto-optical storage system capable of writing over previously recorded information in a single pass without the problems of dimensions and access times found in other optical storage systems .

According to a first aspect of the invention, there is provided an optical read / write storage system for reading out or writing in a flexible optical over magneto-optical medium data, respectively, provided with an optical read / write head for providing a sharp spot of light on the flexible medium and for receiving reflected light therefrom; and of fine stabilizing members which cooperate with or are connected to the optical head and positioned close to the flexible medium and serve to stabilize the flexible medium in a desired position so that the optical head is practically not facing the medium or need to be moved from there to keep the light spot on the medium sharp.

According to a second aspect of the invention there is provided an optical read / write storage system for reading out or writing in a flexible or magneto-optical medium data, respectively, provided with an optical read / write head for emitting focused light to the flexible medium and detecting light emanating from the flexible medium; and fine stabilizers cooperating with or connected to the optical head and positioned close to the flexible medium such that the optical head is practically 8900611 / -8- * not toward or there. needs to be moved away to keep the light focused on the medium.

According to a third aspect of the invention there is provided a read / write information storage system for reading from and writing in a flexible magneto-optical medium, respectively, provided with a magnetic recording member having a recording head close to the medium is positioned to record information in a point, which point is defined as the area of the medium in which information is recorded at a given time; and an optical read / write device for providing a sharp spot of light on the medium during reading and writing, for receiving light reflected to the medium for reading the information and for continuously supplying the sharp spot of light on that medium for heating the point while the magnetic recording means is recording.

Embodiments of an optical information storage system according to the invention may be capable of either reading from or writing into optical media at speeds comparable to magnetic storage systems, may have a low weight optical head assembly, and easily manufactured with dimensions that meet the half-height standard.

From the embodiments described herein, it will be apparent that an optical or magneto-optical information storage system may be provided that eliminates the need for a dynamic focusing mechanism by accurately stabilizing a flexible optical medium during read / write operations, wherein the stabilization is achieved at a primary and a secondary level, both of which involve floating the medium on an air cushion created by the Bernoulli principle.

The invention will now be described by way of example only with reference to the accompanying drawings, in which:

Pig. 1 is a perspective view of an optical information storage system according to the invention;

Fig. 2 is a schematic representation of the storage system; FIG. 3 is a perspective view of a portion of the system shown in FIG. 1;

Fig. 4 is a sectional view taken along line IV-IV in FIG. 3;

Fig. 5 is an enlarged view of part of the view shown in Fig.

3 coupling piece shown; 8900611 / * -9-

Fig. 6 is a schematic representation of the optical components shown in FIG. 3;

Fig. 7 is a side view of another exemplary embodiment of the optical components shown in FIG. 6; FIG. 8 is a top view of yet another embodiment of the optical components shown in FIG. 6?

Fig. 9 is a side view of yet another exemplary embodiment of the optical components shown in FIG. 6;

Fig. 10 is a perspective view of a portion of the magneto-optical information system version of the system shown in FIG. 1?

Fig. 11 is a sectional view along line XI-XI in FIG. 10?

Fig. 12 is an enlarged view of a portion of the coupling piece and the magnetic head shown in FIG. 10? and

Fig. 13 is a side view of another embodiment of the magneto-optical system.

An information storage system constructed in accordance with the principles of the invention is shown in Fig. 1 and generally indicated by 10. A container 12 is shown partially inserted into the disk drive housing 14 so that the sliding lid 16 started can be moved sideways. When such lateral displacement has been completed, an opening 18 (shown in Figures 2 to 4) will be released through which the flexible medium plate 20 can be processed.

25 in the plate 20, a central hub 22 is arranged to be gripped by the drive shaft 24 when the holder 12 is fully inserted into the housing 14 to rotate the plate 20. The bottom plate 26 in the housing 14 is shown in partial cut-open form to open the needle element 28 which serves to guide the holder 12 during insertion and the arm 30 during access to the plate 20. Although not fully shown in Figure 1, a head assembly 32 mounted on the distal end of the arm 30. A linear drive motor 34 serves to move the arm 30 into the needle element 28 so that the head assembly 32 is placed radially across the surface of the plate 20.

While several types of linear drive motors are available for use in the invention, it is preferable that the linear drive motor selected is capable of providing both coarse and fine displacements of the arm 30 for both finding an 89 0 0 611 * -10 track as following the track through the head assembly 32. The range of displacement of the arm 30 is from the retracted position shown in Fig. 1 to an extended position such that the distal end arm 30 touches stop 36.

The details of the construction of the container 12, in particular its integrally formed Bernoulli surface and its insertion and tackling by the various plate drive components as described above, are more fully disclosed in U.S. Pat. Nos. 4769733, 4740851, 4743989, 4740851, 4658318 10 and U.S. Patent Applications 854342 filed April 21, 1986, 854333 filed April 21, 1986 and British Patent Application No. 2190232. It further discloses U.S. Patent Application 947682 filed December 20, 1986, which is related to with U.S. Patent 4,658,318. Since this patent application 15 primarily relates to magnetically recorded information storage systems, the media (the applications describe the use of double floppy discs in a single container) and the means for reading and writing data from or in the medium are different. Incidentally, the construction used in these devices will be practically identical to that which can be included in a storage system according to the invention. It is believed that a single floppy disc can be substituted for the double medium described in the aforementioned patent applications.

A commercially available player / holder for magnetically recorded information that can be modified to obtain an optical or magneto-optical information storage system according to the invention, the Beta-20 system is manufactured and marketed by IOMEGA Corporation , Roy, Utah, USA. It will be appreciated that the circuitry and programming used in the Beta-20 system 30 to convert the analog signals generated by magnetically captured information into a digital signal requires modification so that the analog signals generated by optically recorded information generated, can also be converted into a digital signal. And the technique for converting such optically generated analog signals to digital signals is known.

Let us now consider the optical information storage system schematically shown in Fig. 2. The disc drive motor 40 rotates the plate 20. This rotation is started by an appropriate start signal from a processor 42. While the plate 20 is rotating, the 89 0 0 6 1 1 3-11 processor 42 supplies a start signal to a linear motor 34 which drives the optical head assembly 32 into the radial direction across the surface of the plate 20. The head assembly 32 illuminates a limited area on the plate 20 with a light beam in a manner to be described below in response to yet another start signal from the processor 42. Information recorded on the plate 20 modulates it at the surface light reflected from the plate 20, which reflected light is detected and converted into an electrical signal by the head assembly 32 and this signal is supplied to the processor 42. There are several known methods for accomplishing this operation and the invention is not limited to the use of a particular method. Similarly, the invention is not limited to using any particular method of recording information on the plate 20. The processor 42 rotates the plate 20 rapidly, the linear motor 34 rotates the head assembly 32 radially across the plate. 20 and let the head assembly 32 write the desired information on the surface of the plate 20.

In case the system is a magneto-optical system, in the preferred embodiment the conversion to an electrical signal of the reflected light is effected using a differential detection scheme. It is recalled that light that is either reflected on a magneto-optical plate or passed through it at a point where information is inscribed will have slightly different polarization than the light directed at the medium. The change in polarization will be either clockwise or counterclockwise depending on the orientation of the north pole at that point. By passing the reflected light through a beam splitter, detecting both split beams and comparing the detected beams, it is possible to determine if the reflected light has changed its polarization, which indicates the presence of a indicates captured digital 1. Since this type of detection scheme has been described with reference to another magneto-optical device in Mansuripur, M. et al, "Signal and noise in magnetoptical readout," Journal of Applied Physics, Volume 53, No. 6 (June 35, 1982). pp. 4485-4493, no further details will be given here.

Figures 3 to 9 relate to an optical information system. As shown in Fig. 3, the holder 12 is fully inserted and the arm 30 is extended to such an extent that the optical head assembly 32 is displaced across the surface of the plate 20 in radial direction.

The optical head assembly 32 is indicated by a laser diode 44 with lead wires 46. Although not shown, it will be understood that the lead wires 46 are electrically connected to the processor 42 2 for operating it in one of several known ways.

The laser diode 44 serves as a light source for the optical head assembly 32. As used herein, light is understood to mean both visible and invisible light, or more precisely, electromagnetic radiation.

More particularly, the term "light" is intended to include light having a wavelength in the range of 200 to 2000 nanometers (nm).

As indicated in Figures 3, 4 and 6, the light emitted from the laser diode 44 is passed through an aperture plate 48 which serves to limit the diameter of the beam or collimate it to a desired size in the preferred embodiment 1 ζ is equal to the smallest allowable beam diameter in the optical system. Light passing through the aperture plate 48 is further collimated through a lens 50 and fed to a polarizing beam splitter 52 where the light is reflected toward or toward the plate 20. The light reflected from the polarizing beam-20 splitter 52 is then passed through a quarter-wavelength wafer 54 which, as is known, acts to change the polarization plane of the light. After reflection, the light going back through the quarter-wavelength wafer 54 will have the polarization plane left by 90 ° and thus the light will pass through the mirror surface in the beam splitter 52 and will not be reflected back to the diode 44.

Light passing through the quarter-wavelength plate 54 to the plate 20 will then pass through the lens 50, after which the light is focused on the surface of the plate 20. Unlike in known optical storage systems, the lens 56 is not on a Mounted in such a way that it is moved relative to arm 30. In this regard, the lens 56 is stationary with respect to the arm 30. Light reflected or emanating from the surface of the plate 20 is then collimated through the lens 56 and passed through the quarter-wavelength wafer 54. As previously described, since its polarization plane is now 90 ° delayed, the light will pass through the beam splitter 52 and be focused through the lens 58 on the detector 60. The lenses 56 and 58 may be gradient index lenses.

Although the detector may have 60 different designs, a particular detector used is the model IT338, manufactured and marketed by Sony Corporation 89006 1 1-‑13. Such a detector serves to detect, i.e. distinguish, both data and track-tracking information. The detector 60, in turn, generates electrical signals that display or indicate the detected data information and tracking information. These signals are then transferred via processor wires 62 to the processor 42. As a result, the signals from the detector 60 serve not only to provide the information accessed, but also to allow the processor 42 to process the tracking information and to provide or supply the appropriate signals 10 to the linear motor 34 for moving the arm 30 in such a manner that the optical head 32 can be positioned radially above a desired track on the plate 20 and follow this track. The lens 56, as shown in Fig. 4, is securely mounted in a connector 64 which in turn is securely mounted in the arm 30.

While not shown, it will be appreciated that an opaque cover member may be disposed over the optical head assembly 32 to exclude stray light as well as to protect the optical head assembly 32 from the environment as well as from dust. .

The lens 56 can be mounted stationary in the arm 30 because it is not necessary to dynamically focus the light from the diode 44. The need to perform dynamic focusing has been eliminated due to the amount of stabilization provided to the plate 20, and the predictability of the distance between the plate 20 and the lens 56 during operation. Such stabilization and predictability come from two sources, namely the plate 56 which is arranged in the holder 12 in the preferred embodiment, and the coupling piece 64.

The plate 66 provides a primary stabilization, while the coupling piece 64 allows a secondary stabilization of the medium. The surface of the plate 66 opposite the information carrier 20 is a Bernoulli surface which serves to establish and maintain an air cushion between the information carrier and the plate 66. The constructional features which create this air cushion by 35 of the Bernoulli surface are known and will not be repeated here. However, adapting such phenomena to optical information storage systems in order to meet the need for dynamically focusing light on the data carrier is not known.

Although the disc 66 in the preferred embodiment has been described as 89 0061 1: a part of the holder 12, it is within the scope of the invention that the disc 66 is physically attached to the disc drive 10.

In such an alternative embodiment, the holder 12 will be constructed such that the plate 66 is positioned adjacent the disc 20 after fully inserting the holder 125.

Although the disc 20 is primarily stabilized by the air cushion generated by the plate 66, it is recalled that the optical head assembly 32 has access to the disc 20 through the aperture 20. The aperture 18 is also provided in plate 66.

10 in the region within the opening 18, there is no stabilization of the disc 20. As a result, the connector 64 serves to provide local secondary stabilization in the region around the lens 56 by generating and maintaining an air cushion. keep in mind that portion of the disk 20 should hold that continues below the coupler at a short distance and as will be described in: a predictable relationship thereto. Although the details of the structure contained in the coupling piece 64 for achieving air cushion generation have been described in U.S. Pat.

4414592, the adaptation of such phenomena to optical information storage systems to eliminate the need for dynamically focusing light on the disc is not known. Referring to Fig. 5, the surface of the coupling piece 64 creates and maintains an air cushion between the coupling piece 64 and the disc 20. In the preferred embodiment, the distance "A" between the connector and the disk is about 5 to 10 microns plus or minus 0.5 microns. There are a number of alternative shapes and constructions of the coupling that allow the required stabilization of the medium to be obtained. In a particular construction, the relationship between the coupling piece 64 and the disc 20 is achieved by providing a substantially flat surface 70 surrounding the lens 56 (not shown), as well as a series of increasingly steeper surfaces that are attached to the surface. 20 limits. It will be noted that in Fig. 5 these surfaces cannot be easily distinguished and some degree of exaggeration of the curved shaped surfaces is necessary. In the preferred embodiment, the surface 72 is a curved surface formed with a radius of curvature of about 500 mm, the surface 74 is also a curved surface with a radius of curvature of about 270 mm and the surface 76 is a generally flat conical surface which is formed at an angle of approximately 45 ° to the surface 70. bok will be noted that the radii of curvature selected for the surfaces 72 and 74 will differ depending on the properties of the selected medium such as stiffness, flexibility and the presence and properties of lubrication. The radius of curvature of the lens 56 (not shown in Fig. 5) and the distance by which the lens 5 protrudes from the surface 70 also depend on the properties of the selected medium. In the preferred embodiment, the radius of curvature of the lens 56 is about 50 mm and protrudes about 0.02 mm above the surface 70.

It is important to note that the construction of the coupling piece 64 can be used to stabilize either rotating flexible disks, such as the disk 20, or tape embodiments of an optical medium. This construction is necessary only to obtain and maintain an air cushion between the optical head contained in the coupler 64 and the medium that is either rotated or moved in a straight line along the coupler 64 or otherwise, it is scanned helically by means of a revolving drum in geometric proportions known from the magnetic data recording technique. Furthermore, it may be necessary to provide the plate 66 for Bernoulli stabilization 20 of a rotating disk. Indeed, such stabilization is not necessary for a tire-shaped medium. Therefore, the invention can be applied to both flexible optical disks and flexible optical tape material.

Referring to Fig. 7, there is shown another embodiment of the optical head assembly than in. Fig. 6. Light passing through the lens 50 is supplied to a prism 80 which is a combination of an anamorphic correction prism and a polarizing beam splitter prism. In order to reduce the dimensions of the optical head assembly, it was found that some degree of anamorphic correction was necessary for the light emitted from diode 44 (not shown). The shape of the prism 80 is chosen so that the first optical axis is perpendicular to the last optical axis. Also, an objective lens 82 is substituted for the lens 56 with a gradient index as shown in Fig. 6. It has been found that the objective lens provides better aberration correction of the 55 wavefront than the lens with a gradient index. A polarizing beam splitting top layer 84 is provided to reflect the light to the lens 58. The polarization plane of this light is then delayed by the quarter wavelength wafer 54.

Referring to Fig. 8, there is shown a top view of 0900011? 6 -16- another embodiment of the optical head assembly shown in Fig. 6. In the same manner as the assembly shown in Figure 7, an objective lens 82 is provided for focusing light on the medium 20 (not shown in Figure 8). A prism 84 is provided whereby the lens 58 and lens 50 can now be positioned side by side, further reducing the height of the optical head assembly. A polarizing beam splitting cover layer 88 is again applied to reflect light towards the lens 58. A mirror surface 90 serves as a folding mirror for totally reflecting light from either the prism 86 to the lens 82, or from the lens 82 to the prism 86.

Referring to Fig. 9, yet another alternative embodiment of the optical head assembly shown in Fig. 6 is given. There may be circumstances where it is desirable to provide a focusing effect. For this purpose, the laser diode 44 is securely mounted on a solenoid-like member 92. However, the lens 50 and beam splitter 52 are mounted on the plunger 94 by support members 96. The member 92 is constructed such that the distance between the lens 50 and diode 44 can be optionally changed by applying an appropriate signal to line 98 through processor 42. Such a signal will be provided in response to the signal detected by processor 42 from the signal supplied by detector 60. 20 setting the need to focus the light. Methods for performing such determinations are currently known in connection with dynamically focused optical systems. Light emitted from the beam splitter 52 is then reflected by a mirror surface prism 98 through a quarter-wavelength wafer 54 and a lens 56 toward the surface of the disc 20.

Figures 10 to 13 relate to a magneto-optical storage system according to the invention. In the following description, parts of interest for the magneto-optical aspect of the invention are denoted by reference numerals greater than 100. As shown in Figure 10, the holder 112 is fully inserted and the arm 130 is extended so far that the magneto-optical head assembly 132 has been radially displaced across the surface of the disc 120. It will be appreciated that the arm 130 is split into an upper arm half 130a and a lower arm half 130b with the disc 120 passing therebetween. The magneto-optical head assembly 132 is shown as split between 89006-1. -17- the arm halves 130a and 130b for supporting the optical and magnetic portions of the head assembly. First consider the optical portion of the head assembly supported by the arm half 130a in which a laser diode 144 with lead wires 146 is indicated. Although not drawn, it will be understood that the lead wires 146 are electrically connected to the processor 42 (see FIG. 2) for operating it in one of a number of known ways. The laser diode 144 serves as a light source, the term "light" having the meaning discussed above.

As indicated in Figures 10 and 11, the light emitted from the laser diode 144 is passed through the lens 150 and collimated thereby. Subsequently, this light is passed through the polarizing beam splitter 152, after which it is presented to the prism 154 and is reflected on or from the mirror surface 155 towards or in the direction of the disc 120. The lens 150 can be a lens with a gradient index. The light reflected from the prism 154 is then passed through the lens 156 which focuses the light onto the surface of the disc 120. Unlike in known magneto-optical storage systems, the lens 156 is not mounted in such a way that it is displaced relative to the arm 130. In this regard, the lens 156 is stationary in relation to the arm 130. Light that is reflected on or from the surface of the disc 120 is then collimated again by the lens 156, by prism 154 is passed and reflected by the mirror surface present in the beam splitter 152. Since the light is reflected on or from the surface of the disc 120, the detection will depend on the Kerr effect. The polarization plane of the light reflected on the medium, called the "reading beam", has two possible orientations depending on the orientation of the magnetic moment in the reflection point on the medium. The polarization plane of these two orientations of the reflected light is rotated a few degrees from the polarization plane of the illuminating beam. The read beam is collimated again by the objective lens 156 and reflected back by the prism 153 to the beam splitter 152. In the preferred embodiment, the beam splitter 152 is a nicely polarizing beam splitter that has not only the polarization component of the read beam that has been established due to the rotation effect of the medium, it will also reflect some of the stronger polarization component of the light that is in the original plane of the illuminating beam,

8900611V

-18- will reflect. As a result, the portion of the read beam reflected by the beam splitter 152 is a substantially constant fraction of the total strength of the read beam incident on the beam splitter 152, but the difference in rotation between the two possible polarization orientations are exaggerated. The reading beam then passes through a half-wavelength wafer 157 to the beam splitter 158, a polarization beam splitter that splits the light into two constituent beams that are focused by the lenses 159a and 159b on a detector 160a and 16B, respectively. Lenses 156 and 159a and 159b can be gradient index lenses. The half-wavelength wafer 157 serves as a rotator to rotate the polarization planes of the read beam about 45 °, adjusted so that, on average, the strengths of the reflected beam and the transmitted beam from beam splitter 158 are equal again.

Although detectors 160a and 160b may have a number of different designs, a particular detector used is the model IT338 which is manufactured and marketed by Sony Corporation. Such a detector serves to detect or distinguish both data and tracking information. The detectors 160a and 160b, in turn, generate electrical signals that display or indicate the detected data information and tracking information.

These signals are then transmitted via processor wires 162 to the processor 42. As previously explained, the signals from both detectors are compared in the processor 42 to determine whether there is a difference between the signals. The difference between the signals is an indication of the sign of the magnetic domain and therefore of the logical state recorded in the reflecting point on the disc 120. For example, a positive difference is an indication of a digital 1 that is in that point recorded, while a negative difference is an indication of a digital 0 recorded in that point.

The signals from the detectors not only serve to provide access to information, but also allow processor 42 to process tracking information and provide the appropriate signals to linear motor 134 or supply it of appropriate signals to move the arm 130 so that the magneto-optical head 132 can be radially positioned over a desired track on the disc 120 and track it. The lens 156 is rigidly mounted in the support plate 164 which are on turn is firmly mounted in the arm half 130a.

»900611 -19-

A magnetic head 170 is securely mounted in the lower arm half 130b. By moving the medium between the magnetic head 170 and the lens 156, information can be magnetically recorded on the disc 120 at those points heated by the light focused by the lens 156.

The lens 156 and the magnetic head 170 may be stationary mounted in the arm 130 due to the elimination of the need to dynamically focus the light emerging from the diode 144. The need to dynamically focus this light has been eliminated due to the degree of stabilization given to the disc 120, and the predictability of the distance between the disc 120 and the lens 156 in operation. Such stabilization and predictability come from two sources, namely the plate 166 which is arranged in the holder 112 in the preferred embodiment, and the magnetic head 170. The plate 166 provides a primary stabilization, while the magnetic head 170 provides a secondary stabilization of the medium. The surface of the plate 166 facing the disk 120 is a Bernoulli surface that serves to create and maintain an air cushion between the disk and the plate 166. The constructional features that create the this air cushion resulting from the Bernoulli surface is known and will not be repeated here. However, adapting such phenomena to magneto-optical information storage systems to eliminate the need for dynamically focusing light on the disc is not known.

Although the plate 166 in the preferred embodiment is shown as an integral part of the holder 112, in another configuration the plate 166 may be physically attached to the disc drive 110. In this alternative construction, the holder 112 has been appropriately modified with the plate 166 can be placed close to disk 120. As a result, once the holder 112 is fully inserted into the disc drive 110, the operation of the Bernoulli surface of the plate 166 in providing the primary stabilization of the disc 120 is substantially identical to that described above. .

While not drawn, it will be appreciated that an opaque cover member may be disposed over the magneto-optical head assembly 132 to exclude stray light as well as protect the magneto-optical head assembly 132 from the environment , as well as against dust.

Although the disc 120 is stabilized by the air cushion that 89 0 0 61 1.11.

-20- generated by the plate 166, it is recalled that the magneto-optical head assembly 132 accesses the disk 120 through an opening 18. The opening 18 is also present in the plate 166. In the area inside the opening 118, there is no stabilization of the disc 120. As a result, the magnetic head 170 serves to provide local secondary stabilization in the area surrounding the lens. 156 environs, by creating and maintaining an air cushion that serves to hold the portion of the disc 120 and the magnetic head 170 close together and in an imaginable manner as they pass each other. While the particularities of the structure contained in the magnetic head 170 for obtaining air cushion generation have been described in U.S. Patent 4,441,592, the adaptation of such phenomena to magneto-optical information storage systems is to eliminate the need for dynamically focusing light on the disc is not known.

Referring to Fig. 12, the surface of the coupling piece or of the magnetic head 170 creates an air cushion and maintains this air cushion between the magnetic head 170 and the plate 120. In the preferred embodiment, the distance "A" between the head and the disc is approximate 5 to 10 microns plus or minus 0.5 microns. There are a number of alternative shapes and constructions of the coupling that allow the required stabilization of the medium to be obtained. In one such construction, the relationship between the magnetic head 170 and the disc 120 is achieved by providing the magnetic head 170 with a practically flat surface 171 surrounding the lens 156 (not shown), and with a series of increasingly steeper surfaces that adjoin on the surface 171. It will be noted that in Figure 2 such surfaces cannot be easily distinguished and some degree of exaggeration of the curved shaped surfaces is necessary. In the preferred embodiment, the surface 172 is a curved surface formed with a radius of curvature of 500 mm, the surface 174 is also a curved surface with a radius of curvature of 500 mm, the surface 174 is a curved surface with a radius of curvature 270 mm and the surface 176 is a generally planar surface which is formed at an angle of 45 ° to the surface 171. Although not shown in Fig. 12, the same secondary stabilizing means can be provided for the optical head assembly . In particular, stabilization around the lens 156 can be achieved by creating a similar set of curved shaped surfaces for the connector 164 surrounding the lens 156. Thus, it is within the scope of the invention to provide such stabilization on either the magnetic head 170 or the coupling piece 164 or on both.

It is important to note that the construction magnet head 170 and connector 164 can be used to stabilize either rotary flexible disks, such as the disk 120, or hand shapes of magneto-optical media. This construction is necessary only to obtain and maintain an air cushion between the magnetic head or connector and the medium being rotated, moved in a straight line along the magnetic head, or helically scanned by a rotating drum in geometric conditions known in the magnetic data recording technique. Furthermore, it may not be necessary to provide a plate 166 for Bemoulli stabilization of a rotating disk. After all, such stabilization is not necessary for a band-shaped medium. Therefore, the invention applies to both magneto-optical discs and magneto-optical tape material.

Since the surface of the disc 120 is stabilized at a relatively fixed distance from the magnetic head 170, it is possible for the first time to operate a magneto-optical storage system so that the magneto-optical head focuses continuous light on the surface of the disc 120. As a result, information is recorded on the disc 120 by changing the orientation of the magnetic field of the magnetic recording element of the magnetic head 170. Since the magnetic head 170 is of a size used for magnetic recording of information on so-called floppy discs, the problem of relatively slow switching of the orientation of the magnetic field existing in known devices has been eliminated.

Referring to Fig. 13, an alternative embodiment 30 of the magneto-optical head assembly is shown there. Instead of splitting the arm 130 into an upper half and a lower half, it may be desirable to position the magnetic recording head 170 and the optical head on the same side of the disc 120. Since the aim is to make a magnetic recording in the same place, the magnetic head 170 is provided with a U-shaped magnetic element 180. Although not shown, it will be appreciated that the magnetic element 180 is an electromagnet to which the magnetic field is given in accordance with an electrical signal supplied over the lead wires 182. Light to be focused on the surface of the 89.0.061-22 disc 120 is passed between the arms 184a and 184b of the element 80. The height of the magnetic head 170 will have to be taken into account. That is, since the magneto-optical head will be slightly further from the disc 120, this distance must be taken into account when choosing the lens 156.

Now consider the magneto-optical information storage system during the write and read operations. During a write operation, the information to be written on the flexible medium is organized by the processor 42 for sequential recording on the disk 120. A signal is generated by the processor 42 that activates the laser diode 144, assuming the processor 42 has determined from the signals from the detectors 166a and 166b and that the magneto-optical head assembly is positioned above a desired track on the disk 120. When the laser diode 44 is activated, information to be written is recorded on the disk 20 by varying the orientation of the magnetic field of the magnetic head 170, all this in a known manner. Since the disc 120 is heated at the point where the light is focused from the laser diode 144, the poles placed in that heated area on the medium will assume the orientation of the magnetic field supplied by the head 170. Such a reorientation of poles on the disk 120 will continue until the processor 42 has written all the information to be recorded. Obviously, while this write-in operation is taking place, the disc 120 rotates rapidly about the hub 22 and the linear motor 34 moves the arm 30 so that the magneto-optical head assembly 132 is moved radially across the disc 120, also in response to signals from the processor 42.

During the readout operation, light from the laser diode 144 is focused on the surface of the disc 120. It is not necessary and indeed it is preferred that the energy associated with the light upon reading is such that the heating of the disc 120 by the light is minimal. Light reflected from the surface of the disc 120 passes through the magneto-35 optical head in the manner already described and results in a series of electrical signals generated and fed to the processor 42. The processor 42 determines the difference between the signals from detectors 160a and 160b and uses this result to determine the presence of a logic 1 or a logic 0 stored on the 890061 f disk.

-23- 20 have been recorded. In fact, if the processor 42 detects a difference in the signals from the detectors 160a and 160b, a logic 1 is present on the medium. If there is no difference between the signals, a logic 0 is present on the medium.

It will be apparent to those skilled in the art that the invention can be modified without departing from its principles described herein. For example, in an alternative and not shown embodiment, the linear drive motor 34 can be replaced by a rotary drive motor. Such a member would move across the surface of the disc 20 in a manner similar to that of the arm movement of a conventional gramophone. Thus, in such an embodiment, the arm 30 and the needle element 28 will not have the shape shown in Figure 1 but will be appropriately modified to allow accurate positioning and displacement of the head assembly 32 over the surface of the disc. 20 is possible.

8900611

Claims (15)

1. Optical read / write storage system for reading out or writing in a flexible optical or magneto-optical medium of data, respectively, characterized by an optical read / write head for providing a sharp light spot on the flexible medium and for receiving reflected light therefrom; and by fine stabilizing members co-operating with or connected to the optical head and positioned close to the flexible medium and serving to stabilize the flexible medium in a desired position so that the optical head is practically not facing the medium or it is necessary to move from there to keep the light spot on the medium sharp. 2. Optical read / write storage system for reading out or writing in a flexible optical or magneto-optical medium of data, respectively, characterized by an optical read / write head for emitting focused light to the flexible medium and detecting from light emanating from a flexible medium; and by fine stabilizers co-operating with or connected to the optical head and positioned close to the flexible medium so that the optical head practically does not need to be moved toward or away from the medium to keep the light focused on the medium. Storage system according to claim 1 or 2, characterized by a coarse stabilizing member, positioned close to the flexible medium, for providing a coarse stabilizing effect to the flexible medium when reading and writing data, wherein the coarse stabili The lisating member has an opening that provides access to the flexible medium. 4. Optical read / write storage system for reading from 8900611. -25- respectively writing in a flexible medium of data, characterized by a coarse stabilizing member, positioned near the flexible medium, to provide a coarse stabilizing effect. on the flexible medium when reading and writing data, said coarse stabilizing member having an opening providing access to the flexible medium; a light source for providing light of a kind suitable for reading and writing information in, respectively, the flexible medium; 10 a polarizing beam splitter positioned to receive the light from the source; a displacement member connected to the beam splitter for positioning the beam splitter above the flexible medium so that the light from the source is reflected to the flexible medium; an optical phase delay means positioned near the beam splitter for transforming the polarization of the light as the light passes through it; a lens member positioned near the retarder 20 and serving to focus the light falling on the flexible medium through the retarder and to collect light reflected on the flexible medium and supply it to the retarder; a detector member positioned near the beam splitter 25 for receiving the reflected light and generating an information signal in response to such reception; and a fine stabilizing member connected to the beam splitter and positioned near the flexible medium and serving to stabilize the flexible medium in a desired position so that the lens does not need to be moved substantially towards or away from the medium in order to light it up keep the medium focused. 5. Device for reading out and / or writing in a flexible carrier which is enclosed in a holder and is provided with optically detectable data, wherein the holder has an opening through which the flexible carrier can be accessed, characterized by means for receiving and placing a container with the opening therein in a predetermined position; an optical system adapted to focus a light beam on a predetermined plane so that when the holder is inserted into the receptacle 8900611. -26- the light beam falls through the opening in the holder and the predetermined plane is within the circumference of the holder is; means for rotating the flexible support about an axis substantially perpendicular to its plane; and a Bernoulli effect member for locally bending the flexible support in the region of the aperture so as to bring the curved portion of the support into a practically stable coincident relationship with the predetermined plane whereby the light beam can be kept focused on the carrier without the optical system having to be adjusted during the rotation of the carrier. Device according to claim 5, characterized in that the Bernoulli effect member comprises a coupling piece with a surface adapted to fit into the opening when the container is inserted into the receiving member, the surface of which the coupling piece surrounds the light path of the light beam through the coupling piece, The device according to claim 5, characterized in that the Bernoulli effect member includes a coupling piece with a surface arranged to align with the opening when the 2Q holder is inserted into the receiving member, wherein the connector is placed on the other side of the flexible carrier from the optical system. 8. Device as claimed in claim 7, characterized in that the coupling piece is provided with magnetic means for use in effecting the reading and / or writing in of magneto-optical data. 9. Device according to claim 5, characterized in that the Bernoulli effect member comprises a first coupling piece with a surface adapted to coincide with the opening when the container is inserted in the receiving member, and a second connector with a surface adapted to align with the opening when the container is inserted into the receiving member, the first connector and the second connector positioned on either side of the predetermined focusing plane of the light beam. Device according to any one of claims 5 to 9, characterized in that a Bernoulli plate cooperates with the receiving member to effect coarse stabilization of the rotating support, the Bernoulli effect member providing fine stabilization provided from a portion of the support where the surface of the support extends through 8900611 -27- the opening. 11. Device for reading and / or writing a flexible carrier tape with optically detectable data, characterized by a read / write assembly provided with an optical system arranged to focus a light beam on a predetermined plane; means for transporting the tape along a path passing through the read / write assembly; and a Bemoulli effect means for locally bending the flexible tape in the vicinity of the read / write assembly so as to bring the bent portion of the carrier practically in stable coincident relationship with the predetermined plane through which the light beam can be focused held on the tape without the need for adjustment of the optical system as the tape advances along the read / write assembly. Device according to claim 11, characterized in that the Bemoulli effect member comprises a coupling piece with a surface placed in the region of the read / write assembly and over which the tape is passed as the tape passes through the read / write assembly passes. Device according to any one of claims 6 to 10 and 11, characterized in that the coupling piece or the coupling pieces have a boundary where the surface of the coupling piece bends away from the predetermined plane. 14. Device according to claim 12, characterized in that the boundary surface consists of a number of surface parts of different slope or radius of curvature. 15. An information read / write storage system for reading and / or writing data on, respectively, from a flexible magneto-optical medium, characterized by: 30 a magnetic recording member with a recording head which is next to the medium. positioned, for recording information on the medium at a point where the point is defined as the area of the medium in which information is recorded at any time; and an optical read / write means for providing focused light on the medium during reading and writing, for receiving reflected light from the medium for reading out information, and for continuously providing focused light on the medium. for heating the point while the 3900611. -28 magnetic recording device is recording. -o-o-o- 890061 1.