JPS63103440A - Method and apparatus for optically recording and reproducing data - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a helical scanning optical device for recording and/or reproducing data.

U.S. Pat. No. 4,525,828 discloses a helical scan optical recording device for data, in which
The writing beam is focused by controlling a final objective lens located on the drum.

The present invention provides an apparatus for optically recording and reproducing data, in which a tape material suitable for recording data in the form of indicia having optical properties different from that of the tape material is sent to a drum around the drum. means for providing a helical scan of the portion of the tape material at a wrapping location on the drum; means for dynamically focusing said light onto said portion of said tape material at said wrapping location, said focusing means being disposed in a light path between said light supply means and said drum; A device for optically recording and reproducing data is provided.

In this way, the focusing action of the device of the invention is substantially unaffected by centrifugal forces caused by rotation of the drum.

The focusing means is a pupil-relay pair.
The number of parts, which is preferably provided with means for changing the spacing between the lenses (ypair), can be kept low to keep the cost of the device low. Advantageously, said spacing changing means comprises a voice coil actuator comprising a focusing lens acting as one of the pupil-relay pair lenses.

Preferably, said focusing means operates in dependence on an output from a monitoring means for light following a helical scan, said monitoring means being a detector which can be used in a read mode to reproduce the read output signal. Advantageously, it comprises an array of.

In use, an air bearing is preferably provided between the drum and the portion of tape material in the winding position.

Advantageously, the tracking means comprises a galvanometer pivoted mirror arranged on the drum.

Alternatively, the tracking means comprises a non-pivotal mirror disposed on the drum and movable along the optical path.

The device of the present invention provides an indicia (ind) representing data.
means for providing a plurality of light beams for writing indicia) on the tape material and/or means for providing a plurality of light beams for reading indicia representing data in the tape material; means U1 for relative rotation about an axis parallel to the path of the drum, the rotation means being arranged in the optical path between the light supply means and the drum and at a speed of rotation of the drum. Preferably, the rotation speed is dependent on the rotation speed.

The indicia on the tape material representing the data may have any suitable form, for example consisting of transparent areas on a reflective or non-transparent tape or reflective or non-transparent tape on a transparent tape. It may also be a sexual area.

The invention also provides an apparatus for helical scanning recording and/or reading of data on optical tape, comprising:
Also provided is an apparatus for use in the present invention.

According to another JLi 18, the present invention provides a method for optically recording and reproducing data, including feeding a tape material suitable for data recording to a drum as an indicia having optical properties different from that of the tape material. said means for wrapping substantially around said drum and directing said light to said portion of said tape material at said drum wrapping location for a helical scanning of said portion of said tape material; , dynamically focusing the light output from the light supply means onto the portion of the tape material at the wrapping location, and including means for the focusing in the optical path between the light supply means and the drum. A method for optically recording and reproducing data is provided.

Preferably, the focusing means includes changing the spacing between the pair of pupillary lenses.

Preferably, the method comprises monitoring the light following the helical scanning and operating the focusing means in accordance with the results of this monitoring step.

Preferably, the method includes providing an air bearing between the drum and the portion of tape material at the wrapping position.

Preferably, the method includes tracking light on a drum to scan the portion of tape material at said pick-up location.

The method includes reading indicia representing data on the tape material and relatively rotating the light beams about an axis parallel to their path, the relative rotation being relative to the light supply means. Preferably, the rotational speed is carried out in an optical path between the drum and the rotational speed is dependent on the rotational speed of the drum.

Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, a rotating drum 1 is constructed to include a galvanometer-mounted mirror 2 and a final objective lens 3 fixed inside the drum. 1 drum
having a diameter on the order of 10 mm and rotating at a substantially constant rotational speed, typically in the range of 50 to 150 revolutions per second, and typically having a circumferential speed of 17 to 52 meters per second during recording or playback. The reflective optical recording tape T having 0 reflectivity is usually 30 to 30
The tape is transported along a helical path around the drum in a substantially 340'' ohm wrap at a substantially constant linear velocity in the range of 0 fl/sec. operating at such speeds creates an air bearing at the interface between the tape and the drum, which in real equipment would , due to small changes in tape tension, tape speed and drum rotation speed, some variation in the spacing between the opposing surfaces of the tape and drum is likely to occur.The writing and reading laser beams pass from the fixed mirror 4 through the focusing lens 5. is directed to a galvanometer mirror 2 and deflected through a final objective lens 3 on the drum onto the surface of the optical tape T. Each write and read beam is subjected to the above-mentioned variation in tape-to-drum separation. Dynamic focusing control is provided to ensure that the focusing lens 5 is focused to form a diffraction-limited spot, typically less than 1 micron in diameter, on the tape surface, which is controlled by a voice coil type actuator 6.
This is achieved by servo-controlling the position of the A voice coil type actuator is used to control the focusing of the final objective lens in an optical disk device, and a suitable configuration for this purpose is described, for example, in “Principles of Optical Disk Devices” by Adam Hilgler, published in 1985, by G. Bouhuis et al.
It is described on pages 136-142. The drum may be a reel or drum as is known from helical scan magnetic tape technology.
It can be used in a two-reel type tape transfer device or a cassette type tape transfer device.

In detail about the optical configuration, N independently modulated 850n so that N information trunks can be simultaneously written on the tape by N coplanar writing beams.
A linear array of m lasers is provided. single 780
A nm reading laser 8 is provided, the reading laser beam being split into N+1 coplanar beams by a beam splitting grating 9, following collimation by a collimator lens IIB, so that N+1 information trunks can be read simultaneously. Ru. FIG. 1 is a configuration for the N-5 case, where N can be on the order of 2 and 50. The write lasers are typically all energized simultaneously and independently modulated during write operations, ie, recording operations, and the read lasers are energized during read, ie, playback operations. If the recording medium is of a type that requires processing between write and read operations, such as photoresist or other photographic media, the write and read lasers are typically not activated at the same time ( , so writing and reading cannot be performed simultaneously.

If the medium is of a type that allows instantaneous regeneration, such as a heat-absorbing abrasive film or dye, the write and read lasers must be used to allow verification and reading during the write operation in direct read while writing (DRDW) mode. At the same time, it is energized. The optical system of the present invention will be explained in the DRDW operation mode.

The writing and reading lasers have different optical wavelengths, with each writing laser typically having a wavelength of 850 nm and the reading laser having a wavelength of 780 nm. The writing laser beam is concentrated by a concentrator 1o and a collimating lens IIA to form five equally spaced, coplanar light beams, which are deflected by a fixed mirror 12 to a dual prism beam combiner. Enter 13. The read laser beam, which has less power than the write beam, is collimated and split into six coplanar beams which are passed through polarizing beam splitter 14.
and is sent to the beam combiner 13 through the quarter wavelength plate 15. Five reading beams and six writing beams are sent through an optical image rotator 2° to a fixed mirror 4, and then deflected and focused by a rotating drum onto a galvanometer mirror 2 to form a diffraction-limited spot on the surface of the recording medium. form. Lenses 16 and 5 form a pair of pupil relay lenses through which both the writing and reading beams pass, and a fixed lens 17 is provided between grating 9 and beam splitter 14. 0
The optical system of the present invention, as shown enlarged in FIG. It is made to match. Each write spot has sufficient intensity to form an abrasion-resistant recording focus on the medium, and the read spot has a lower intensity.The read laser is reflected from the medium and passed through an optical system to a polarizing beam splitter. and then the interference filter 1
8 through a known Li-like beam and a lens 18A.
6 in-line photodiodes Do~D by
is focused onto an array of 5. The interference filter ensures that only light reflected from the read laser and not from the write laser is sensed by the photodiode array.

If no optical rotator is provided, this optical system will work satisfactorily with only one writing beam or one reading beam approaching the galvanometer mirror along the axis of the drum. The separated beams will cause a change in the spacing of the tracks on the recording medium due to the rotation of the galvanometer mirror 2 on the drum.

A solution to this problem is provided by suitably rotating the effective object source for the write and read beams. Optical rotation devices that, when rotated, produce rotation of an image about an optical axis are known, such as the Dove, Schmidt, Eizo, Bee Block, and Pechan rotators, which rotators, when rotated, produce a rotation of the image. Gives an image of a stationary object rotating at twice the rotation speed of the body. An optical rotator 20 is provided through which the writing and reading beams pass in accordance with the beam combination. This optical rotator is driven by motors 21A and 21B so that it rotates synchronously at half the rotational speed of the drum, thereby imparting an image to a recording medium that rotates synchronously with the drum.

The image formed on the medium corresponding to the reading beam is the first
It has the form of six (N+1) in-line diffraction-limited spots NO to N5 shown in the figure.

The 5 (N) write beams are connected to the 5 read beams.
It is focused on a spot that overlaps spots N1 to N5.

During the writing operation, the angle α1 is set with respect to the spot line.
Five parallel tracks T1 to T5 are recorded on the tape, and in a read operation, the previously recorded adjacent track TO is used as the read spot N for trunk position control.
It can be read by O. The galvanometer mirror 2 is held in a fixed position during a write or read sweep, and the recorded track follows the tape edge through a small angle known as the sweep angle α2, which is governed by the slope of the tape helix around the drum. I'm doing it for you.

If a rotor is not provided, a galvanometer
Due to the image rotation caused by the rotation of the mirror, the angle α1 will change during scanning, and thus the spacing between tracks on the tape will change in an unacceptable manner; this change causes the optical rotator 20 properly synchronized to half the rotational speed of the drum, the image rotation caused by the rotor cancels out the image rotation caused by the drum, effectively creating a constant angle α1 and a constant track distance. This is done to create a spacing.

In a read operation, the read beam reflected from the tape surface passes through the drum in the opposite direction of the incident beam before being deflected by polarizing beam splitter 14 towards an array of sensing diodes 19 and optically The rotator compensates for image rotation caused by rotation of the galvanometer mirror, and the alignment of the deflected beams and their associated sensing diodes is maintained.

An optical rotator 20 is placed between the lenses 16 and 5 forming the pupil-relay pair and allows the focusing lens 5, controlled by the voice coil, to be moved closer to the periphery of the drum. FIG. 1 shows the rotator placed between the lens 16 and the fixed mirror 4; alternatively, the rotor may be placed between the fixed mirror and the focusing lens 5, in such a position. The light beams in FIG. 1 are shown as parallel for ease of illustration, although they tend to converge or diverge significantly. Therefore, suitable rotors that are perpendicular to the rotor population and the direction of exit facepiece rotation are preferably Bee block, Eizo, and Pechan types, and the more commonly used Dub and Pechan types. Schmidt rotors have tapered inlet and outlet faces and are therefore less permeable for use in the present invention.

The embodiment of the invention shown in FIG. 1 uses a known polarizing beam splitting system for the read beam, in which the incident read beam and the reflected read beam are polarized. The incident beam is first split linearly by a polarizing beam splitter 14 and then converted to circularly polarized light by a quarter-wave plate 15. The reflected beam has a polarization orthogonal to the polarization of the incident beam. It is in a circularly polarized state on the return path until it is converted to linearly polarized light by a quarter-wave plate with a 1/4 wave plate, and then deflected by a polarizing beam splitter towards a diode array. In such a system, the incident and reflected read beams are ideally circularly polarized as they enter and leave the rotor. Internal reflections within the rotor preferably do not introduce undesirable polarization effects that adversely affect the circularly polarized light in order to avoid excessive periodic amplitude modulation of the sensed reproduction signal.

Optical rotators of the conventional type described above generally include one or more suitably shaped optical prisms, and the optical path through such a rotator has an odd number of reflections. Generally, some or all of the reflective surfaces in this optical path are total internal reflection surfaces. Light that undergoes total internal reflection typically experiences significant polarization effects, whereas light reflected from metal surfaces is generally much less susceptible to such effects.

A side view of a rotator suitable for use with a polarized reading beam is shown in 2nd UjJ. This rotor has the form of a single prism with only three reflective surfaces, all metallized, and no total reflective surfaces, this prism is in the form of a bee block. It has a rectangular cross section ABCD, and its top surface is V like an AED.
It is cut into a letter shape. ■The depth h of the cut is usually half the height AB of the block, and the block is
’. Block surfaces AE and ED
and the central region GE of the lower surface is metallized with, for example, vapor-deposited silver 1 with a central axis along the axis of rotation XX'
or more light beam enters the surface AB of the prism,
It is then reflected by the three metallized surfaces and exits the prism with their central axes unchanged. As the prism rotates, the image formed by the beam emerging from it rotates about the axis 1xx' at twice the rotational speed of the prism in a known 1I3i manner. Alternatively, the prism may have a cross section AFGHT D as shown in FIG.
It may have the shape of an Azo rotor as shown by E. Although Figure 2 shows only three beams entering and exiting the prism, the axis of rotation XX
' usually coincides with the midpoint of the N+1 planar reading beams in the above-mentioned optical reading device.

Although the use of polarizing beam splitters and quarter-wave plates is advantageous in preventing polarized read beams from being directed partially toward the read laser, such polarizers are not essential. However, due to economic reasons,
Known optical playback devices, such as many compact disc players, operate using non-polarizing semi-uniform mirrors instead of polarizing beam splitters and do not use quarter-wave plates. Non-polarized reading optics may be used, in which case a rotor such as a conventional Bea-block, Azo or Pechan type with one or more total internal reflections is undesirable for periodic amplitude modulation. It can be used without causing any problems. The Pechan rotor has the advantage of being axially symmetrical. The rotor is
It is normally attached to a hollow shaft 21A driven by a motor 21B to rotate about the axis &IXX'.

Control the deflection of galvanometer 2 during write and read operations? 1, and control leads (not shown) in the hollow shaft 22 supporting the drum are provided to control track positioning. The leads communicate via slip rings or inductive couplers with control lines that can be externally energized to select a particular index track position, and one or more of the diodes DO-D5 It communicates with galvanometer control leads for servo-controlling track position in a known manner. In the preferred embodiment shown in FIG. 1, in communication with the galvanometer, and during the first write/read scan, a first band consisting of five trunks T1-T5 is written and by diodes DO-D5. Read simultaneously in DRDW mode. In the second scan, the galvanometer picks up the reading light spot N.

is superimposed on the just written track T5 and during this second scan the diode DO is superimposed on this track T5.
During this time, the second track consisting of tracks T1 to T5 is detected.
The galvanometer Do will be indexed so that the band is written and sensed by the diode DO-D5, the signal from the diode Do will be indexed to the galvanometer so that the first recorded track T5 is followed precisely. Processed to dynamically control deflection.

One or more of the diodes Do-D5 are in communication with the voice coil actuator 6 to dynamically control the position of the last pupil relay lens 5 and to adjust the spacing between the drum and the tape as described above. When a change occurs, the associated light spot on the tape is brought into focus (imaged).

The circuits and mechanisms used for focusing and indexing servo control I and for track position servo control during writing and reading are well known in optical disk recording technology, such as those described in the above-mentioned book by G. Bouhuis. Generally similar to the method used.

A suitable ffl control device for implementing control of the rotational speed and relative phase of the drum and optical rotors in multi-beam recording and relaying is shown in FIG. The hollow drive shafts associated with the optical rotor and drum are provided with shaft encoders 23 and 24, respectively. The drum rotational speed is first defined by an input signal of constant reference frequency F r*t+ and is controlled by a first phase-locked control circuit (P L
Through L), a signal representing the drum rotational speed is divided in frequency and controls the rotational speed of the rotor. During reading, the read signals from the diodes Do and D5 corresponding to the outer tracks To and T5 are passed through the detector logic and appropriate up/down integration logic (clocked at a constant frequency FrafN) to a second phase lock. The output of this PLL provides a drive signal to the motor that drives the rotor.

Signals from the drum shaft encoder and the rotor shaft encoder are provided to a relative phase m unit to maintain predetermined control of the phase between the drum and rotor motor.

Other embodiments of the invention will be apparent to those skilled in the art. For example, a single write channel may be used for simultaneous reads from multiple read channels. Alternatively, a single high power writing laser can be used whose output beam is split into N multiple beams that are independently modulated.

This embodiment of the invention provides a multi-beam helical scan optical recording and playback device capable of accessing multiple tracks simultaneously during recording and/or playback, thereby increasing data throughput rates. I will provide a. This embodiment also provides a helical scan optical recording and playback device capable of direct read on write (D RD W) operation.

4 and 5 illustrate another, more concise, single-trunk scheme according to the present invention, which has one optical power level for writing data and another for reading data. A laser 40 having two optical output levels is included. Such a scheme can be used in read-only mode with low power lasers.

In the operation of the optical recording system shown in FIGS. 4 and 5,
The light from the semiconductor laser 40 passes through the final rotating imaging objective lens 4.
1 onto a thermosensitive recording medium in the form of an optical tape T. The write-only or read-only medium can be a photoresist film that is suitably chemically treated between write and read operations. The operation of the writing mechanism is such that a pulse of energy from laser 40 operating at a writing level abrades one area of the heat sensitive area on the base film to form a bit. 1/4 wavelength plate 42
and sensing optics forming a polarizing beam splitter prism 43 images the reflected beam onto a detector array 44 which outputs a read output signal, an imaging error signal and a tracking error signal. give.

Electronic sensing methods similar to those in optical disc technology are applied to the diode signals to form control signals used to control a galvanometer 45 disposed on the rotating drum. Electronic sensing methods are also possible, whereby a single beam is mechanically modulated by a galvo at a high frequency (>60 kHz), in which case the sensed signal is processed to give an error control signal. It's a signal.

The apparatus uses a voice coil actuator 47 and lens 48 operated on an imaging error signal to dynamically image light onto the tape T. Lenses 49.5, 51 and a fixed mirror 52 are also provided to properly guide the light beam.

In the case of helical scanning, changes in drum speed
Change the static pressure in the tape gap and thus change the head/tape gap. Without mechanical compensation methods to accommodate this variation, data corruption will occur because the signal-to-noise ratio is directly related to the head/tape gap.

In the case of optical recording, it is required that a definable gap exists between the final imaging lens and the recording medium. In optical disk technology, this is achieved by driving the final imaging objective with a mechanically driven voice coil. To protect the optical recording layer, a transparent plastic protective layer is coated on the media and the laser beam is imaged through this layer. Since bulges and other obstructions are not imaged, their impact on the signal-to-noise ratio is reduced. In the case of photosensitive media, B is the same as magnetic recording tape.
protection requirements are significantly reduced. The media can be wrapped in layers and stored in a cassette. Therefore, to protect the medium, it is only necessary to control the atmosphere and keep it free from contact imaging during recording and reading. With a helical optical recording head,
Three conditions are immediately satisfied. The drum generates a clear air bearing that is directly related to it's rotational speed. Therefore, changes in drum/tape spacing, or working distance, are compensated for by lenses elsewhere in the device.
To reduce rotational forces, this lens is placed directly above the entrance orifice to the drum.

By using the above arrangement, it is possible to vary the data rate in both write and read cycles without relying on electronic recording methods. Changes in drum rotation speed can be compensated by a combination of galvo tracking to accommodate changes in track angle, and a focusing voice coil can compensate for changes in objective working distance caused by changes in static pressure. can be compensated.

All of the embodiments described above are modified so that instead of the galvanometer mirror, the drum is provided with an objective lens and a non-pivot mirror that move synchronously with each other along the optical path, as shown in FIG. I can do it. A magnetic or piezoelectric quadratic transducer 60 for tracking in direction (2) is used to position the final imaging objective 61 by virtue of the electronic determination error signal that drove the galvanometer. Here, the error signal is used to position the objective lens at a desired track position determined on the basis of an external command, i.e., a preselected trunk address or a signal determined from an individual trunk error position. lens 61
A prism mirror 62 is provided fixedly on a mounting member 63 for a smaller optical displacement from the vertical displacement of the final imaging objective, rather than changing the direction of the beam entering the final imaging objective. A system arises.

The helical scan optical tape recording and reproducing apparatus shown in FIGS. 4 and 5 has a rotating drum equipped with a galvanometer mirror to control the tracking of a single beam of light during recording and playback. , in which case the dynamic focusing of the beam on the recording medium is controlled by a voice coil actuator acting on a lens placed outside the drum.The device shown is capable of operation at high recording densities. is limited to the use of a single write or read beam that enters the drum along the drum axis, and simultaneous recording or playback with multiple beams will result in rotation of the image imaged onto the tape surface. resulting in undesirable changes in trunk spacing.

The present invention provides a system that has the high data density and signal-to-noise ratio of optical disk systems and the excellent flexibility and storage volume efficiency of tape systems. This method can be advantageously utilized when a huge storage capacity ft (arehieval 5 tore) is required. I can do it.

In the case of the optical tape system, there is an inertia gain because the tape has a clearly smaller mass than the disk transporter in the carousel.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the basic optical and mechanical components of a multi-beam optical recording and reproducing device; FIG. 2 is a side view of an optical image rotator; FIG. FIG. 4 is a block diagram showing a control device, FIG. 4 is a schematic diagram of an apparatus according to another embodiment of the present invention, FIG. 5 is a diagram showing the drum of FIG. 4, and FIG. 6 is a diagram showing another type of drum. be. In the drawing, 1 is a rotating drum, 2 is a pivoting mirror, 3 is a final objective lens, 6 is a voice coil actuator,
7 is a laser array, 8 is a reading laser, 9 is a beam splitting grating, 5.16 is a pupil/relay pair lens, and 20 is a rotor.

Claims (1)

[Claims] 1. In a method for optically recording and reproducing data, a tape material suitable for recording data as an indicia having optical properties different from that of the tape material is sent to a drum, and the tape material around the drum is substantially wrapping the tape material around the drum and causing a helical scan of the portion of the tape material by outputting light from means for providing light toward the portion of the tape material at the wrapping location of the drum; dynamically focusing light output from a means onto said portion of said tape material at said wrapping location, said means for said focusing being disposed in a light path between said light supply means and said drum; A method for optically recording and reproducing data. 2. The method of claim 1, wherein the focusing step includes changing the pupil-relay-to-lens spacing. 3. A method according to claim 1 or claim 2, comprising monitoring the light following the helical scanning and operating the focusing means in accordance with the result of this monitoring step. 4. A method as claimed in one of claims 1 to 3, comprising providing an air bearing between the drum and the portion of the tape material at the winding location. 5. A method as claimed in one of claims 1 to 4, comprising tracking a light in a drum for scanning the portion of the tape material at the winding location. 6. A method as claimed in one of claims 1 to 5, in which a plurality of light beams are provided for writing indicia representing data on a tape material and/or on said tape material. providing a plurality of beams for reading indicia representing data of the light beams, rotating said light beams relative to each other about an axis parallel to their paths, and said rotation causing a rotation between said light supply means and a drum. and having a rotational speed dependent on the rotational speed of the drum. 7. In an apparatus for optically recording and reproducing data, the tape material suitable for recording data in the form of indicia having optical properties different from that of the tape material is sent to a drum and substantially surrounded by the drum. means for helically scanning the portion of the tape material by supplying light toward the portion of the tape material at the wrapping location of the drum; and light output from the light supplying means. means for dynamically focusing the data onto said portion of said tape material at said wrapping location, said focusing means being disposed in a light path between said light supply means and said drum. A device that optically records and plays. 8. The apparatus of claim 7, wherein said focusing means comprises means for varying the pupil-relay-to-lens spacing. 9. Apparatus according to claim 7 or 8, wherein the focusing means is operable in dependence on an output from a means for monitoring light following helical scanning. 10. Device according to one of claims 7 to 9, in which an air bearing is provided between the drum and the portion of tape material at the winding location. 11. Apparatus according to one of claims 7 to 10, wherein the drum is provided with means for light tracking for scanning the portion of tape material at the winding location. said device. 12. Apparatus according to one of claims 7 to 11, comprising means for providing a plurality of light beams for writing indicia representing data on the tape material; and and/or means for providing a plurality of beams for reading indicia representing data on said tape material and means for relatively rotating said light beams about an axis parallel to their path. , the rotation means being arranged in the optical path between the light supply means and the drum and having a rotation speed dependent on the rotation speed of the drum.