CA1085050A - Method for recording information on a rotatable medium - Google Patents
Method for recording information on a rotatable mediumInfo
- Publication number
- CA1085050A CA1085050A CA268,574A CA268574A CA1085050A CA 1085050 A CA1085050 A CA 1085050A CA 268574 A CA268574 A CA 268574A CA 1085050 A CA1085050 A CA 1085050A
- Authority
- CA
- Canada
- Prior art keywords
- disc
- information
- track
- record medium
- pattern
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
- G11B7/128—Modulators
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B23/00—Record carriers not specific to the method of recording or reproducing; Accessories, e.g. containers, specially adapted for co-operation with the recording or reproducing apparatus ; Intermediate mediums; Apparatus or processes specially adapted for their manufacture
- G11B23/0014—Record carriers not specific to the method of recording or reproducing; Accessories, e.g. containers, specially adapted for co-operation with the recording or reproducing apparatus ; Intermediate mediums; Apparatus or processes specially adapted for their manufacture record carriers not specifically of filamentary or web form
- G11B23/0021—Record carriers not specific to the method of recording or reproducing; Accessories, e.g. containers, specially adapted for co-operation with the recording or reproducing apparatus ; Intermediate mediums; Apparatus or processes specially adapted for their manufacture record carriers not specifically of filamentary or web form discs
- G11B23/0028—Details
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/007—Arrangement of the information on the record carrier, e.g. form of tracks, actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track
- G11B7/00736—Auxiliary data, e.g. lead-in, lead-out, Power Calibration Area [PCA], Burst Cutting Area [BCA], control information
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
- G11B7/08547—Arrangements for positioning the light beam only without moving the head, e.g. using static electro-optical elements
- G11B7/08564—Arrangements for positioning the light beam only without moving the head, e.g. using static electro-optical elements using galvanomirrors
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0901—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following only
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/095—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble
- G11B7/0953—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble to compensate for eccentricity of the disc or disc tracks
Abstract
RECORD MEDIUM, METHOD OF MAKING SAME, AND METHOD AND APPARATUS FOR RECORDING
INFORMATION ON AND REPRODUCING INFORMATION
FROM SAID RECORD MEDIUM
ABSTRACT OF THE DISCLOSURE
A novel record medium, its method of manufacture, and a method and apparatus for recording information on and reproduc-ing information from said record medium are disclosed. The record medium comprises a disc-like body having a surface pro-vided with a first portion adapted to have signal information recorded thereon and a circular track distinct from the first portion having reference information therein. When used to record signal information in the first, or signal information portion thereof, the record medium is rotated about an axis while the signal information is recorded thereon. The refer-ence information in the circular track is predetermined, detectable pattern which is sensed while the record medium ro-tates. In the event of eccentric rotation, the record medium undergoes a lateral displacement with respect to a center, or drive shaft, whereby the circular track is shifted with respect to a fixed pattern detecting station. This, in turn, results in a relative shift in the detectable pattern whereby the eccentric rotation is sensed. The signal recording apparatus is adjusted in response to sensed eccentric rotation so as to compensate for such rotation. Similarly, when the record medium is used for the reproduction of previously recorded information, eccentric rota-tion of the medium is sensed by detecting a shift in the detect-able pattern provided in the circular track so as to correspond-ingly adjust the signal playback apparatus to compensate for such eccentric rotation.
-i-
INFORMATION ON AND REPRODUCING INFORMATION
FROM SAID RECORD MEDIUM
ABSTRACT OF THE DISCLOSURE
A novel record medium, its method of manufacture, and a method and apparatus for recording information on and reproduc-ing information from said record medium are disclosed. The record medium comprises a disc-like body having a surface pro-vided with a first portion adapted to have signal information recorded thereon and a circular track distinct from the first portion having reference information therein. When used to record signal information in the first, or signal information portion thereof, the record medium is rotated about an axis while the signal information is recorded thereon. The refer-ence information in the circular track is predetermined, detectable pattern which is sensed while the record medium ro-tates. In the event of eccentric rotation, the record medium undergoes a lateral displacement with respect to a center, or drive shaft, whereby the circular track is shifted with respect to a fixed pattern detecting station. This, in turn, results in a relative shift in the detectable pattern whereby the eccentric rotation is sensed. The signal recording apparatus is adjusted in response to sensed eccentric rotation so as to compensate for such rotation. Similarly, when the record medium is used for the reproduction of previously recorded information, eccentric rota-tion of the medium is sensed by detecting a shift in the detect-able pattern provided in the circular track so as to correspond-ingly adjust the signal playback apparatus to compensate for such eccentric rotation.
-i-
Description
- l~J8SO~iO
BACKGROUND OE THE INVENTION
This invention relates generally to a record medium and, more particularly, to a disc-like record medium, a method of its manufacture and a method and apparatus for recording information on and reproducing information from that record medium. In use, the record medium is rotated, and a particular aspect of this invention is to permit accurate signal recording -~and reproduction from that medium despite eccentric rotation that might be present.
A rotatable record medium has been used for many years for the recording and reproduction of information. Examples of -such a medium include the well-known phonograph disc wherein ; information is recorded thereon in the form of mechanical undulations which are sensed by a suitable transducer, such as a stylus, and converted into audible sounds. Information is recorded on the phonograph disc by creating a master disc and then stamping multiple copies therefrom. In the master disc, audible sounds are converted into corresponding electrical signals which, in turn, drive a suitable transducer, such as a recording stylus, to effect the various undulations in a generally spiral track about the axis of rotation of the master disc. Another example of a disc-like record medium is a magnetic disc which can be used to record video information, audio information or digital information on its surface. In the - magnetic disc, signal information can be recorded either in a substantially continuous spiral track or in concentric circular tracks. Yet another example of a disc-like record medium is the so-called video disc. In one embodiment of the video disc, video signals and audio signals are recorded in the form of an ; 30 irregular surface modulation, such as pits or grooves, such modulation being optically detectable. In another embodiment of the video disc, surface modulation is detected by a suitable ~-stylus.
-` lOB5VSO
In general, when a disc-like record medium of the character described is used, it is rotated with respect to a transducer by a suitable driving mechanism, such as a turntable, rotary shaft, or the like. Occasionally, the record medium undergoes a lateral displacement, that is, a shift in a generally radial direction, resulting in eccentric rotation. This lateral displacement may be caused by fluctuations in the rotary drive mechanism. For example, if the record medium is provided with a central hole or aperture along its axis of rotation, a significant amount of play between that hole and the drive shaft or guide shaft inserted therein will result in such a lateral shift and eccentric rotation.
When information is recorded in concentric circular tracks on the disc-like record medium, the transducer that scans the record medium for signal recording or reproduction ideally should scan a perfect circular track. However, eccentric rotation of the disc will result in corresponding deviations in the scanned track. In a similar manner, if the record medium is provided with a spiral information track of predetermined pitch, the transducer that-scans the record medium for signal recording or reproduction should define a spiral track identical to that pitch. However, eccentric rotation of the disc will result in an irregular pitch of the scanned track. Generally, deviations in the track actually scanned by the transducer from the ideal track are not readily noticeable in phonograph records. That is, eccentric rotation of the disc during manufacture of the master or during playback of a copy is not easily detected. miS is because the width and pitch of the information track is relatively large in comparison to the eccentric rotation.
Conversely, when information track density must be high, such as in a magnetic disc or in a video disc, an eccentric rotatiOn is 108S050 : ~
, :
readily sensed as distortion in the recording or reproduction of information. As an example, if the width of an information track is in the range of about 1 to 3 ~m, and if the pitch is about 2 to 3 ~m, then lateral shifts in the disc, or eccentric rotation, should be restricted to between 0.1 and 0.5 ~m.
Eccentric rotation due to fluctuations in the drive mechanism of the disc can, in many instances, be satisfactorily controlled. Also, fluctuations in the transducer drive mechanism which will result in an irregular pitch likewise can be controlled satisfactorily in many instances. Unfortunately, an irregular pitch in the information track caused by fluctuations in the drive shaft for the disc heretofore has been controlled only by resorting to very expensive machining -techniques in the construction of the drive mechanism.
OBJECTS OF THE INVENTION
Therefore, it is an object of the present invention -to provide an improved record disc which can be used to compensate for the formation of an irregular pitch in the information track during signal recording or reproduction.
Another object of this invention is to provide an improved record disc for the recording or reproduction of infor-mation without distortion despite eccentric rotation of the disc.
A further object of this invention is to provide an improved record disc having a predetermined circular track which is used as a reference to establish a proper information track during signal recording or reproduction despite eccentric rotation of the disc caused by a lateral shift thereof.
An additional object of this invention is to provide a method of manufacturing a record disc of the character described.
--` 10850S~
Yet another object of this invention is to provide a method and apparatus for accurately recording or reproducing information from a record disc despite lateral shifts in the rotation of the disc resulting in an eccentric disc rotation.
Various other objects, advantages and features of the present invention will become readily apparent from the ensuing detailed description, and the novel features will be particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
In accordance with this invention, a novel disc-like rotatable record medium is provided with a first portion adapted to have signal information recorded thereon and a separate circular track distinct from the first portion having reference information therein; the reference information being usable to establish an accurate scanning path for a recording or reproducing transducer.
It is one aspect of this invention to provide a method of recording information on the foregoing disc-like record medium by recording suitable signal information thereon during rotation of the medium so as to form an information track, detecting a predetermined pattern provided in the circular track to sense eccentric rotation of the medium, and adjusting the ,formation of the record track in response to sensed eccentric rotation to compensate for such eccentric rotation. Another :~
aspect of this invention is to manufacture a master record disc from the foregoing information-recorded medium.
Yet another aspect of this invention is to provide a method and apparatus for recording and/or reproducing information from a record disc of the foregoing character -30 whereby such information is recorded and reproduced substantially without distortion despite lateral shifts, or eccentric rotation, of the record disc. ~
More particularly, t~ere is provided: ~ -A method of recording signal information on a rotatable record medium having a circular track thereon provided with a detectable predetermined pattern, comprising the steps of rotating said record medium about an axis which is at least approximately concentric with the center of said circular track thereof; recording said signal information on said record medium during rotation of the latter thereby to form an information track; continuously detecting only said predetermined pattern in said circular track during said rotation of said record medium to sense any eccentricity of said circular track in respect to said axis of rotation;
and adjusting the formation of said record track in response to sensed eccentricity in the rotation of said record medium to compensate for such eccentric rotation and thereby maintain a precisely predetermined relation of said information track to said circular track.
There is also provided:
A method of recording signal information on a record disc of the tupe having a predetermined detectable pattern formed as a circular track on a surface of said disc and a layer of transformable material provided over substantially r j .
. the entire remainder of said surface, comprising the steps of - rotating said disc about an axis which is at least : approximately concentric with the center of said circular track thereof; modulating a carrier with signal information;
exposing said transformable layer with the modulated carrier as said disc rotates to form an information track; continuously . 30 detecting only said predetermined pattern as said disc rotates to sense any eccentricity of said circular track in respect .
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to said axis of rotation thereof; adjusting the formation of said record track by shifting th.e location at wh.ich said modulated carrier impinges on said transformable layer in response to sensed eccentricity of the rotation of said disc to compensate for said sensed eccentricity and thereby maintain a precisely predetermined relation of said information track to said circular track; and developing and fixing said exposed transformable layer on said surface of said record disc to form an irregular surface corresponding to said signal information.
BRIEF DESCRIPTION OF THE DRAWINGS
The following detailed description, given by way of example, will best be understood in conjunction with the accompanying drawings in which:
FIGURE 1 iS a plan view of one embodiment of the record medium described herein;
FIGURE 2 iS a block diagram of signal recording apparatus which can be used with the record medium of FIGURE l;
FIGURES 3A-3D are schematic diagrams which are useful in understanding the operation of a portion of the apparatus depicted in FIGURE 2;
FIGURE 4 is a graphical illustration which is helpful in understanding the control technique used with the apparatus . shown in FIGURE 2;
FIGURE 5 is a block diagram of signal reproducing ; apparatus which can be used with the record medium of FIGURE l;
and FIGURE 6 is another embodiment of a reference track that can be provided on the record medium shown in FIGURE l;
and used wï.th the apparatus shown in FIGURES 2 and 5.
DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS
Referring now to the drawings, wherein like reference numerals are used throughout, and in particular to FIGURE 1, there is illustrated one embodiment of a disc-like record medium 1. Disc 1 is provided with a circular bore or hole 2 adapted to receive a drive or guide shaft about which the disc rotates. The disc also is provided with top and bottom surfaces, one or both of which having a portion 3 adapted to have signal information recorded therein and a circular track 4 concentric with the rotary axis of disc 1 and adapted to have reference information therein, described in greater detail below. In the embodiment illustrated in FIGURE 1, circular track 4 circumscribes information-bearing portion 3. In an alternative embodiment, information-bearing portion 3 circumscribes the circular track. If disc 1 is similar to a phonograph record disc, a substantially spiral information track is provided in ;nformation-bearing portion 3. This ; track has surface undulations which are sensed by a suitable stylus and converted into corresponding electrical signals which, in turn, are transformed into audible sounds during playback. If disc 1 comprises a magnetic disc, information-bearing portion 3 is provided with a substantially spiral information track on which signal information is magnetically recorded in conventional manner; or, alternatively, such signal information is magnetically recorded in successive, concentric circular magnetic tracks. In yet another embodiment, if disc 1 is a video disc, then information-bearing portion 3 is ; formed of a spiral track formed with pits or grooves representing video signal information. As mentioned previously, these - 30 pits or grooves are sensed either optically or by a suitable stylus to recover the signal n~ormation represented as such :
.
pits or grooves.
Circular track 4 is distinct from information-bearing portion 3 and the reference information contained therein is in the form of a detectable predetermined pattern. This pattern is formed of suitable indicia, such as a light-reflective pattern, a magnetically recorded reference signal, an optically detectable pattern, or the like.
As will now be described, the information track or tracks recorded in information-bearing portion 3 is related to circular track 4 such that the distance between any point in the information-bearing portion and circular track 4 is fixed in accordance with a predetermined relation notwithstanding eccentric rotation, or lateral shift, of disc 1 during a signal ; information recording operation. For the purpose of the present description, it will be assumed that circular track 4 i is provided with a light-reflective pattern. However, as will be readily apparent, the reference information provided in this circular track may, alternatively, be constituted by a predetermined magnetic signal. It will also be assumed that information-bearing portion 3 is provided with a spiral signal information track; and that this spiral track is provided with recorded signal information in the form of irregular surface modulations, such as pits or grooves. Disc 1 thus may comprise a phonograph disc or a video disc. As an alternative, information-bearing portion 3 of disc 1 may be provided with magnetically recorded signal information in the form of a spiral track.
Referring now to FIGURE 2, a block diagram is shown comprised of apparatus for recording signal information on information-bearing portion 3 of disc 1. In the illustrated embodiment, disc 1 is to be used as the master disc from which multiple copies are stamped. Disc 1 is comprised of a base 5 upon which a metal film 6, such as aluminum or other light-reflective material, is deposited such as by evaporation.
It is appreciated that film 6 corresponds to circular track 4 shown in FIGURE 1. This circular track has a width of approximately 1 mm. and a thickness of about 0.1 ~m. A slit 7, such as illustrated in FIGURE 3A, is formed in the upper surface of film 6, this slit having a V-shaped groove, as illustrated, or any other suitable configuration to provide a circular discontinuity in the upper surface of the film. This slit has a width of approximately 4 ~m. As will be understood, if light is transmi-tted to impinge upon the upper surface of ; film 6, it will be reflected therefrom along a predetermined path except for that portion of the light that impinges slit 7.
This will be explained in greater detail below.
The top surface of base 5 is provided with a transformable layer 10 of uniform thickness. Disc 1, formed as aforedescribed, is placed upon a turntable 9 having a rotary shaft 8. This rotary shaft is adapted to be inserted into central bore 2 of 20 the disc. Suitable recording apparatus, enclosed within block B, deforms transformable layer 10 with a carrier modulated with signal information as disc 1 rotates. As will be ; described below, the transformable layer may be a photoresist which is exposed to a light beam modulated with signal information, thereby to form a latent image on the photoresist layer of the information to be recorded.
In the illustrated embodiment, recording apparatus B
is comprised of a transducer 22 adapted to scan the upper surface of disc 1 along a predetermined spiral track. To this effect, a suitable drive mechanism, not shown, displaces transducer 22 in a radially inward direction as disc 1 rotates about its axis formed of rotary shaft 8. Although the scanning movement _g_ ' 1~8SOSO
of transducer 22 is related to the rotary movement of disc 1, fluctuations in rotary shaft 8 will result in eccentric rotation of the disc to cause a lateral shift between a given point on the upper surface of the disc and the transducer.
This could result in the formation of an information track that deviates from the predetermined spiral track. In accordance with the apparatus now to be described, the formation ., of the spiral track by transducer 22 is compensated in the event of eccentric rotation of disc 1.
Apparatus enclosed within block A is adapted to sense v a lateral shift in disc 1 during its rotation. In accordance with illustrated embodiment, this apparatus is comprised of a light source 11, opti¢al elements 12, 15 and 16 to focus the light emitted from source 11 onto metal film 6 forming circular track 4, and optical elements 14, 15 and 17 to detect light reflected from the metal film and to sense a lateral shift of disc 8 as a function of a characteristic of the reflected light. Preferably, light source 11 is a He-Ne laser which emits a linearly polarized laser beam. This beam is transmitted to a beam-splitter 12 such that a portion of the emitted beam is transmitted through the beam-splitter to a light detector 13 and another portion of the emitted laser beam is reflected by beam-splitter 12 through a polarized beam-splitter 14, a quarter-wavelength plate 15 and a condenser lens 16. Polarized beam-splitter 14 is matched to the linear polarized direction of laser beam bl reflected from beam-splitter 12. Hence, substantially all of beam bl is transmitted through beam-splitter 14 to quarter wavelength plate 15. The quarter wavelength plate is conventional and is adapted to . 30 transmit a circular polarized beam in response to the linear ; polarized beam applied thereto by beam-splitter 14. Condenser lens 16 focuses beam bl onto metal film 6 in the vicinity of 1()8S(~S(~
slit 7. The focused beam spot produced by lens 16 is approximately 4 ~m.
As will be described, at least a portion of the focused beam is reflected from the surface of metal film 6 through lens 16 and through quarter wavelength plate 15. This reflected light beam is circularly polarized and, consequently, quarter wavelength plate 15 acts upon this circularly polarized beam to produce linear polarization thereof in a direction which is perpendicular to the linear polarization of beam bl that had been transmitted initially to plate 15. The direction of polarization of the reflected beam which now impinges upon beam-splitter 14 is blocked from being transmitted through this beam-splitter and, instead, now is reflected thereby to light detector 17. By properly selecting the polarizing directions of the transmitted and reflected light beams, the same optical elements 14, 15 and 16 can be used to transmit beam bl onto metal film 6 and to reflect the beam that is reflected from this metal film onto light detector 17. Thus, the light transmission and reflection paths traversed between beam- -splitter 14 and metal film 6 are coincident. In an alternative embodiment, separate light transmission and light reflection paths are used.
Light detector 17 is adapted to produce a control signal having a particular characteristic proportional to the intensity of the light beam reflected from metal film 6 and impinging thereon. In a preferred embodim~nt, the magnitude of the control signal is proportional to the intensity of light impinging upon light detector 17. With particular reference to FIGURES 3B-3D, the magnitude of the control signal produced by the light detector is a representation of the magnitude and direction of a lateral shift of disc 1 during its rotation.
' ~
~08SO~U
,, More particularly, let it be assumed that beam bl impinges upon metal film 6 in the vicinity of slit 7 thereon such that a portion bl' is reflected from the top surface of the metal film and another portion bl" impinges upon the slit proper and, consequently, is not reflected along the incident light path.
When disc 1 rotates properly, a predetermined portion bl' (FIGURE 3B~ is reflected from metal film 6. That is, the position of slit 7 during rotation of disc l relative to a fixed reference point, such as a reference point defined by optical elements 12, 14, 15 and 16 is a predetermined position.
~f disc 1 is shifted in a lateral direction, such as in a radially inward direction, slit 7 is displaced relative to the fixed reference point, as shown in FIGURE 3C. Consequently, a greater portion bl' of incident beam bl is reflected from metal film 6. Therefore, the reflected beam impinging upon light detector 17 has a greater intensity, resulting in a control signal of higher magnitude. Conversely, if disc l is laterally shifted in a radially outward direction such that slit 7 is displaced relative to the fixed reference point as shown in FIGURE 3D, substantially none of the incident light beam bl is reflected from metal film 6. Thus, the intensity of reflected light impinging upon light detector 17 is at a minimum, and the corresponding control signal magnitude also is a minimum value.
Variations in -the intensity of the control signal produced by light detector 17 as a function of a detected displacement in slit 7 relative to the fixed reference point, such as occurs during eccentric rotation of disc 1, is graph-ically depicted in FIGURE 4. When the distance between the center-point of slit 7 and the fixed reference point is equal to S, such as when disc 1 rotates properly as depicted in .. . .
~085050 .. .
FIGURE 3B, the magnitude of the control signal produced by light detector 17 is represented as the level T. When the center-point of slit 7 is shifted s-o as to coincide with the fixed reference po;nt, substantially no portion of the incident beam bl is reflected from metal film 6 (FIGURE 3D), resulting in a control signal whose magnitude is a minimum. It is appreciated that, during normal rotation of disc 1, a portion bl' of incident beam bl should be reflected so that the direction of displacement of the disc can be determined by sensing a decrease or increase in the intensity of the reflected beam.
To avoid variations in the control signal produced by light detector 17 as a function of a change in the intensity of the light beam emitted by laser 11, the control signal is "normalized" with respect to the emitted laser beam intensity.
Essentially, this is performed by a divider circuit 18 coupled to receive the control signal produced by light detector 17 and to divide the magnitude of this control signal with the magnitude of a detected output signal produced by light detector 13. In this manner, deviations in the control signal produced by light detector 17 attributed to variations in the intensity of the laser beam emitted by laser 11 are cancelled because such deviations also will appear in the detected output signal produced by light detector 13. This "normalized"
output signal produced by divider circuit 18 is amplified by a preamplifier 19 and supplied to the recording apparatus in block B for the purpose of adjusting the track along which transducer 22 scans so as to compensate for lateral shifts in disc l caused by eccentric rotation thereof.
In the embodiment of the recording apparatus included within block B, signal information is applied to an input ``- 108SOS0 terminal 24a to modulate a carrier, wElereby stylus 22 records the ïnformation-modulated carri`er onto disc 1. If transducer 22 comprises a stylus, the information-modulated carrier corresponds to mechanical vibration of the stylus as determined by the signal information. Thus, the stylus will cut a corresponding groove in the upper surface of disc 1 as the disc rotates and as the stylus scans the disc in, for example, a substantially spiral track. For the embodiment wherein disc 1 comprises a magnetic disc, the carrier is a suitable bias signal that is modulated with signal information, and transducer 22 comprises a conventional magnetic recording head.
In the illustrated embodiment under discussion, transducer 22 comprises an optical, or light-recording, head wherein the carrier is a light beam which is modulated by the signal information applied to input terminal 24a. This signal-modulated light suitably exposes photoresist layer 10 to form a latent image of the signal information, this image subsequently being developed and fixed in accordance with conventional techniques.
As shown in the illustrated embodiment, a suitable light source, such as an Ar laser 23 emits a laser beam which is transmitted to a conventional light modulator 24 whereat signal information applied to input terminal 24a modulates the laser beam carrier. The modulated laser beam b2 is reflected from a suitable reflecting surface, such as mirror 21, and is focused by a condenser lens 25 to form an information-modulated light spot onto the upper surface of photoresist layer 10 on disc 1. This information-modulated laser beam thus scans a substantially spiral track as transducer 22 moves in a generally radially inward direction while disc 1 rotates about its axis. As mentioned previously, in the event of a .
.
:
108S0~(~
radial dïsplacement of disc 1 during its rotation, resulting in eccentric rotation of the disc, the actual information track scanned across the surface of the disc by transducer 22 will vary from its ideal spiral track. Consequently, when information is reproduced from the record disc, or when the record disc is used to make multiple copïes from which information is reproduced, such deviations in the recorded information track will deleteriously affect the reproduced signals, particularly if the disc is not subjected to an a identical eccentric rotation during a signal reproducing operation.
This problem is substantially overcome by adjusting the formation of the signal information record track during recording by shifting the location at which the modulated laser beam impinges photoresist layer 10 of disc 1 in response to sensed eccentric rotation of the disc. This is achieved by ; applying the amplified control signal produced by preamplifer 19 through an additional amplifier 20 to a positioning device for mirror 21. As an example, mirror 21 may be mounted on a ; 20 D'Arsonval movement so that the path along which modulated laser beam b2 is directed is a function of the amplified control signal applied to the D'Arsonval coil. Thus, it may be appreciated that the combination of circular track 4 having metal film 6 and slit 7 therein, together with the sensing i apparatus including light detector 17, and adjustable mirrordevice 21 function as a servo system to maintain the ` information-modulated laser beam b2 at a proper location on ; the surface of disc 1 despite any radial displacement or eccentric rotation of the disc.
The servo control function of the illustrated apparatus will best be understood if it is assumed, in the interest of , .
108505~) simplification, that information-modulated laser beam b2 is adapted to scan a circular information track only. If disc 1 is displaced in a radially outward direction by an amount ~r, the intensity of light reflected to light detector 17 is reduced, as seen in FIGURE 3D. This shift ~r in disc 1 would deviate the circular track scanned by information-modulated beam b2 by a corresponding amount ~r. However, the detected change in light intensity, as sensed by light detector 17, applies a control signal to, for example, the D'Arsonval move-ment to which mirror 21 is mounted, thereby changing thereflecting path along which information-modulated beam b2 is transmitted, resulting in a displacement of the information beam spot on the surface of disc 1 by an amount ~r. Hence, even though disc 1 may be subjected to eccentric rotation, the information track scanned across the surface of the disc is substantially maintained at a correct distance from circular track 4 in accordance with a predetermined relation. Although the foregoing has assumed that this predetermined relation is a fixed distance, that is, the information track is a circular track, it now should be fully appreciated that the instantaneous distance between the point of incidence of information-modulated beam b2 from circular track 4 may vary in accordance with a predetermined function so as to scan a spiral information track across the surface of the disc.
` A similar control operation is performed to adjust the ;` point of incidence of information-modulated beam b2 on the ` surface of disc 1 in the event that the disc is subjected to a radially inward displacement by an amount ~r, such as depicted in FIGURE 3C. In the interest of brevity, description of this operation is not provided.
Once the signal information applied to input terminal ,::
- i~)850S0 24a is recorded in the form of a latent image on the surface of photoresist layer 10 of disc 1 in the manner descrïbed above, the disc can be removed from turntable 9 and developed and fixed in accordance with conventional techniques. This results in the formation of a surface irregularity in the form of pits or grooves corresponding to the light-exposed portions of the photoresist layer. Then, the surface of the photoresist layer, after developing and fixing, is plated with nickel, chromium, or other suitable material. Once plated, the record disc can be used as a master from which multiple copies are stamped.
; Alternatively, and as is conventional, the nickel- or chromium-plated record disc can be used to stamp a master disc from which the multiple copies are produced. In either manufacturing process, it is seen that the surface irregularities formed on ; the surface of disc 1 as a result of exposure of the photoresist layer 10 to information-modulated light will be produced in the copies thereof, these surface irregularities being detectable ; by a suitable transducer so as to reproduce the recorded signal information.
Although the foregoing has described a recording operation wherein disc 1 is provided with a surface layer of a photoresist which is exposed to information-modulated light, it is appreciated that the surface of disc 1 may be provided with a lay-er of other transformable material and a compatible carrier can be modulated to deform such material to form irregular surface undulations representing such information.
For example, the deformable material may be a thermoplastic material, and the carrier used therewith may be thermal energy that is modulated with information to be recorded. As another alternative, the transformable material may be an electrostatic-or electrophotostat;c-sensitive medium, and the carrier may )850S0 be an electric charge that ï.s modulated with. signal information to be recorded or may be an informati.on-modulated light beam adapted to selectively dïssipate a charge provided on the su.rface of such a medium.
Turning now to FIGURE 5, there is illustrated a preferred embodiment of signal reproducing apparatus capable of reproducing the si.gnal information that had been recorded on the information-bearing portion 3 of disc l ~y the apparatus depicted in FIGURE 2 and described above. Accordingly, disc 1 is provided with surface irregularities in the form of undula-. tions, such as pits or grooves, at information-bearing portion 3 and also is provided with a circular track having slit 7 therein. In use, disc l is placed upon a turntable 27 and a rotary shaft 26 is inserted into the central bore of the disc for rotating the record medium. Displacement of disc 1 in the radial direction, as during eccentric rotation, is sensed by the apparatus enclosed within ~lock A. This apparatus is substantially identical to that previously described in ;~ conjunction with FIGURE 2. Hence, in the interest of brevity, . 2Q duplicative explanation here is avoided. Suffice it to say that radial displacement of disc 1 is sensed by detecting the corresponding movement of slit 7 which, as described previously, affects the intensity of the light beam reflected from the circular track to light detector 17, as depicted in FIGURES
.` 3B-3D. Consequently, an amplified control signal is produced by preamplifier 19 having a magnitude proportional to the sensed radial displacement of disc 1.
It is understood that the signal information reproducing apparatus must be compatible wi.th the si.gnal recording apparatus described previously in conjunction with the embodiment shown in FIGURE 2. Accordingly, such signal information reproducing apparatus is adapted to sense the signal information recorded - 1 ~
' 1~8S050 as surface irregularities on disc 1 by transmitting a light beam, such as a laser beam, onto tfi.e surface of the disc and detecting modulations in the reflected light from the disc. To this effect, a light source, such as a He-Ne laser 28 emits a linearly-polarized laser beam that is transmïtted to a beam~spli.tter 29. Beam-splitter 29 is substantially similar to aforedescrib.ed beam-splitter 14 and is adapted to . transmit light therethrough having a linear polarization in a predetermined direction, but to reflect substantially all light that is transmitted thereto having a perpendicularly disposed lïnearly polarized direction.
The laser beam emitter by laser 28 passes through ;. beam-splitter 29 and through a quarter wavelength plate, this plate being substantially similar to aforedescribed quarter wavelength plate 15. Hence, quarter wavelength plate 30 changes . the polarization pattern of the emitted laser beam from a linear polarization to a circular polarization, as is conventional. This circularly polarized light is reflected from a mirror 21 along path b3 a~d is focused by a condenser lens 31 to a beam spot on the surface of disc 1. Light beam b3 impinging upon the surface irregularities of disc 1 is reflected from the disc to traverse the same light path through condenser lens 31 and mirror 21, now in the opposite direction.
This reflected light beam is modulated in accordance with the signal information recorded on disc 1, and is reflected by mirror 21 to pass through quarter wavelength plate 30. The circular polarization of this modulated beam is converted by . the quarter wavelength plate into a linear polarization which now is in a directïon substanti.ally perpendicular to the linearly polarized direction of the laser beam emitted from laser 28. Consequently, this information-modulated light lV8SOSO `
beam is substantially entirely reflected by beam splitter 29 to a lîght detector 32 whereat the modulated signal information is recovered.
For the embodiment wherein mirror 21 and condenser lens 31 comprise a transducer 33 adapted to scan a spiral track across the surface of information-~earing portion 3 of disc 1, a suitable drïve mechanism ~not shown~ is provided to advance the transducer in a radial direction as the disc rotates.
Similarly, if transducer 33 is adapted to scan concentric circular tracks across the surface of disc 1, a suitable driving mechanism is provided to advance the transducer in a radial direc~tion.
As in the previously described recording apparatus, in the event of a radial displacement of slit 7 in circular track 4 caused by eccentric rotation of disc 1, as by fluctuations in rotary shaft 26, the amplified control signal produced by preamplifier 19 and further amplified by amplifier 20 serves to vary the position of mirror 21 so as to correspondingly displace the point of incidence of beam b3 on the surface of disc 1 so as to compensate for such radial displacement. Hence, mirror 21 may be secured to a D'Arsonval movement such that the angular position of the mirror is adjusted as a function of the magnitude of the control signal. Thus, beam b3 impinges upon the surface of disc 1 at a location that is relatively fixed from slit 7 of circular track 4 in accordance with a predetermined relation. As is recognized, for the embodiment wherein signal information is recorded in a spiral track, this "predetermined relation" establishes a spiral scanning track of beam b3-It is appreciated that the control over the location at which beam b3 impinges upon the surface of disc 1 during a signal reproduction operation is substantially identical to the , ~
- ~850S0 : :.
control over beam b2 descri~ed previously with respect to a signal recording operation. Hence, further description of the reproducing apparatus shown in FIGURE 5 need not be described.
It should be recognized that the reproducing apparatus ; which is used to recover the previously recorded signal information should be compatible with the nature of disc 1.
For example, if d;sc 1 is a phonograph disc, transducer 33 is a suitable stylus. Alternatively, if disc 1 is a magnetic disc, transducer 33 is a conventional magnetic reproducing head.
1 10 In the for~going embodiments, it has been assumed that ; the reference information provided in circular track 4 is constituted by slit 7 disposed in a light-reflective material, such as metal film 6. As an alternative embodiment, this reference information may consist merely of a narrow light-, reflective track, such as a track whose width is about 4 ~m.
Still another embodiment of circular track 4 is illustrated in FIGURE 6 as comprising a first circular pattern 5A of uniformly spaced light-reflective elements having a first periodicity, and a second adjacent circular pattern 5B of uniformly spaced light-reflective elements having a second periodicity. Super-imposed on these adjacent circular patterns of light-reflective elements is beam spot 34 corresponding to the focused light beam bl. As is seen, a portion of beam spot 34 impinges upon circular pattern 5A and another portion of the beam spot impinges upon circular pattern 5B. Hence, the intensity of light reflected to light detector 17 includes a first component corresponding to the periodicity of light-reflective elements 5A and a second component corresponding to the periodicity of light-reflective elements 5B. In accordance with the illustrated embodiment shown in FIGURE 6, the first component of the light intensity is of a higher frequency than the second component thereof. When disc 1 rotates properly such that ~ -21-:
.
circular track 4 is located in proper relation with respect to the fixed reference point defined by beam spot 34, the f;rst, or higher frequency component of reflected light will exhibit a first predetermined intensity and the second, or lowe frequency component of the reflected light will exhibit a second predetermined intensi.ty. Any shift in the relative position of circular track 4 with respect to fixed beam spot 34, as by eccentric rotation of disc 1, will alter the respec-tive intensïties of the higher and lower frequency components of the light reflected to light detector 17. This change in .
the respective li.ght intensities is used to produce a control signal corresponding *o the direction and magnitude of a radial shift in disc 1. As before, th;s control signal is ::~-used to adjust the track scanned by transducer 22 or by transducer 33 so as to compensate for eccentric rotation of disc 1.
While the present invention has been particularly shown and described with reference to certain preferred embodiments -thereof, it should be readily apparent that various changes and modi.fications in form and details, such as those suggested hereinabove, as well as others, will be readily apparent to those of ordinary skill in the art. For example, the detectable pattern of indicia forming the reference information provided in circular track 4 may be a predetermined magnetically~
recorded signal, optically detectable indicia, and the like.
Also, recording transducer 22 as well as reproducing transducer 33 may- exhibit the various alternative embodiments described above, or may be differently constructed. For example, these respective transducers may generate an electron beam suitable 3Q for recording and detecting information on disc 1. Therefore, ; it is intended that the appended claims be interpreted as -22~
including all of the foregoin~ changes and modifications in structure snd in use of the aforedescri~ed invention.
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BACKGROUND OE THE INVENTION
This invention relates generally to a record medium and, more particularly, to a disc-like record medium, a method of its manufacture and a method and apparatus for recording information on and reproducing information from that record medium. In use, the record medium is rotated, and a particular aspect of this invention is to permit accurate signal recording -~and reproduction from that medium despite eccentric rotation that might be present.
A rotatable record medium has been used for many years for the recording and reproduction of information. Examples of -such a medium include the well-known phonograph disc wherein ; information is recorded thereon in the form of mechanical undulations which are sensed by a suitable transducer, such as a stylus, and converted into audible sounds. Information is recorded on the phonograph disc by creating a master disc and then stamping multiple copies therefrom. In the master disc, audible sounds are converted into corresponding electrical signals which, in turn, drive a suitable transducer, such as a recording stylus, to effect the various undulations in a generally spiral track about the axis of rotation of the master disc. Another example of a disc-like record medium is a magnetic disc which can be used to record video information, audio information or digital information on its surface. In the - magnetic disc, signal information can be recorded either in a substantially continuous spiral track or in concentric circular tracks. Yet another example of a disc-like record medium is the so-called video disc. In one embodiment of the video disc, video signals and audio signals are recorded in the form of an ; 30 irregular surface modulation, such as pits or grooves, such modulation being optically detectable. In another embodiment of the video disc, surface modulation is detected by a suitable ~-stylus.
-` lOB5VSO
In general, when a disc-like record medium of the character described is used, it is rotated with respect to a transducer by a suitable driving mechanism, such as a turntable, rotary shaft, or the like. Occasionally, the record medium undergoes a lateral displacement, that is, a shift in a generally radial direction, resulting in eccentric rotation. This lateral displacement may be caused by fluctuations in the rotary drive mechanism. For example, if the record medium is provided with a central hole or aperture along its axis of rotation, a significant amount of play between that hole and the drive shaft or guide shaft inserted therein will result in such a lateral shift and eccentric rotation.
When information is recorded in concentric circular tracks on the disc-like record medium, the transducer that scans the record medium for signal recording or reproduction ideally should scan a perfect circular track. However, eccentric rotation of the disc will result in corresponding deviations in the scanned track. In a similar manner, if the record medium is provided with a spiral information track of predetermined pitch, the transducer that-scans the record medium for signal recording or reproduction should define a spiral track identical to that pitch. However, eccentric rotation of the disc will result in an irregular pitch of the scanned track. Generally, deviations in the track actually scanned by the transducer from the ideal track are not readily noticeable in phonograph records. That is, eccentric rotation of the disc during manufacture of the master or during playback of a copy is not easily detected. miS is because the width and pitch of the information track is relatively large in comparison to the eccentric rotation.
Conversely, when information track density must be high, such as in a magnetic disc or in a video disc, an eccentric rotatiOn is 108S050 : ~
, :
readily sensed as distortion in the recording or reproduction of information. As an example, if the width of an information track is in the range of about 1 to 3 ~m, and if the pitch is about 2 to 3 ~m, then lateral shifts in the disc, or eccentric rotation, should be restricted to between 0.1 and 0.5 ~m.
Eccentric rotation due to fluctuations in the drive mechanism of the disc can, in many instances, be satisfactorily controlled. Also, fluctuations in the transducer drive mechanism which will result in an irregular pitch likewise can be controlled satisfactorily in many instances. Unfortunately, an irregular pitch in the information track caused by fluctuations in the drive shaft for the disc heretofore has been controlled only by resorting to very expensive machining -techniques in the construction of the drive mechanism.
OBJECTS OF THE INVENTION
Therefore, it is an object of the present invention -to provide an improved record disc which can be used to compensate for the formation of an irregular pitch in the information track during signal recording or reproduction.
Another object of this invention is to provide an improved record disc for the recording or reproduction of infor-mation without distortion despite eccentric rotation of the disc.
A further object of this invention is to provide an improved record disc having a predetermined circular track which is used as a reference to establish a proper information track during signal recording or reproduction despite eccentric rotation of the disc caused by a lateral shift thereof.
An additional object of this invention is to provide a method of manufacturing a record disc of the character described.
--` 10850S~
Yet another object of this invention is to provide a method and apparatus for accurately recording or reproducing information from a record disc despite lateral shifts in the rotation of the disc resulting in an eccentric disc rotation.
Various other objects, advantages and features of the present invention will become readily apparent from the ensuing detailed description, and the novel features will be particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
In accordance with this invention, a novel disc-like rotatable record medium is provided with a first portion adapted to have signal information recorded thereon and a separate circular track distinct from the first portion having reference information therein; the reference information being usable to establish an accurate scanning path for a recording or reproducing transducer.
It is one aspect of this invention to provide a method of recording information on the foregoing disc-like record medium by recording suitable signal information thereon during rotation of the medium so as to form an information track, detecting a predetermined pattern provided in the circular track to sense eccentric rotation of the medium, and adjusting the ,formation of the record track in response to sensed eccentric rotation to compensate for such eccentric rotation. Another :~
aspect of this invention is to manufacture a master record disc from the foregoing information-recorded medium.
Yet another aspect of this invention is to provide a method and apparatus for recording and/or reproducing information from a record disc of the foregoing character -30 whereby such information is recorded and reproduced substantially without distortion despite lateral shifts, or eccentric rotation, of the record disc. ~
More particularly, t~ere is provided: ~ -A method of recording signal information on a rotatable record medium having a circular track thereon provided with a detectable predetermined pattern, comprising the steps of rotating said record medium about an axis which is at least approximately concentric with the center of said circular track thereof; recording said signal information on said record medium during rotation of the latter thereby to form an information track; continuously detecting only said predetermined pattern in said circular track during said rotation of said record medium to sense any eccentricity of said circular track in respect to said axis of rotation;
and adjusting the formation of said record track in response to sensed eccentricity in the rotation of said record medium to compensate for such eccentric rotation and thereby maintain a precisely predetermined relation of said information track to said circular track.
There is also provided:
A method of recording signal information on a record disc of the tupe having a predetermined detectable pattern formed as a circular track on a surface of said disc and a layer of transformable material provided over substantially r j .
. the entire remainder of said surface, comprising the steps of - rotating said disc about an axis which is at least : approximately concentric with the center of said circular track thereof; modulating a carrier with signal information;
exposing said transformable layer with the modulated carrier as said disc rotates to form an information track; continuously . 30 detecting only said predetermined pattern as said disc rotates to sense any eccentricity of said circular track in respect .
-- ~0850S~
to said axis of rotation thereof; adjusting the formation of said record track by shifting th.e location at wh.ich said modulated carrier impinges on said transformable layer in response to sensed eccentricity of the rotation of said disc to compensate for said sensed eccentricity and thereby maintain a precisely predetermined relation of said information track to said circular track; and developing and fixing said exposed transformable layer on said surface of said record disc to form an irregular surface corresponding to said signal information.
BRIEF DESCRIPTION OF THE DRAWINGS
The following detailed description, given by way of example, will best be understood in conjunction with the accompanying drawings in which:
FIGURE 1 iS a plan view of one embodiment of the record medium described herein;
FIGURE 2 iS a block diagram of signal recording apparatus which can be used with the record medium of FIGURE l;
FIGURES 3A-3D are schematic diagrams which are useful in understanding the operation of a portion of the apparatus depicted in FIGURE 2;
FIGURE 4 is a graphical illustration which is helpful in understanding the control technique used with the apparatus . shown in FIGURE 2;
FIGURE 5 is a block diagram of signal reproducing ; apparatus which can be used with the record medium of FIGURE l;
and FIGURE 6 is another embodiment of a reference track that can be provided on the record medium shown in FIGURE l;
and used wï.th the apparatus shown in FIGURES 2 and 5.
DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS
Referring now to the drawings, wherein like reference numerals are used throughout, and in particular to FIGURE 1, there is illustrated one embodiment of a disc-like record medium 1. Disc 1 is provided with a circular bore or hole 2 adapted to receive a drive or guide shaft about which the disc rotates. The disc also is provided with top and bottom surfaces, one or both of which having a portion 3 adapted to have signal information recorded therein and a circular track 4 concentric with the rotary axis of disc 1 and adapted to have reference information therein, described in greater detail below. In the embodiment illustrated in FIGURE 1, circular track 4 circumscribes information-bearing portion 3. In an alternative embodiment, information-bearing portion 3 circumscribes the circular track. If disc 1 is similar to a phonograph record disc, a substantially spiral information track is provided in ;nformation-bearing portion 3. This ; track has surface undulations which are sensed by a suitable stylus and converted into corresponding electrical signals which, in turn, are transformed into audible sounds during playback. If disc 1 comprises a magnetic disc, information-bearing portion 3 is provided with a substantially spiral information track on which signal information is magnetically recorded in conventional manner; or, alternatively, such signal information is magnetically recorded in successive, concentric circular magnetic tracks. In yet another embodiment, if disc 1 is a video disc, then information-bearing portion 3 is ; formed of a spiral track formed with pits or grooves representing video signal information. As mentioned previously, these - 30 pits or grooves are sensed either optically or by a suitable stylus to recover the signal n~ormation represented as such :
.
pits or grooves.
Circular track 4 is distinct from information-bearing portion 3 and the reference information contained therein is in the form of a detectable predetermined pattern. This pattern is formed of suitable indicia, such as a light-reflective pattern, a magnetically recorded reference signal, an optically detectable pattern, or the like.
As will now be described, the information track or tracks recorded in information-bearing portion 3 is related to circular track 4 such that the distance between any point in the information-bearing portion and circular track 4 is fixed in accordance with a predetermined relation notwithstanding eccentric rotation, or lateral shift, of disc 1 during a signal ; information recording operation. For the purpose of the present description, it will be assumed that circular track 4 i is provided with a light-reflective pattern. However, as will be readily apparent, the reference information provided in this circular track may, alternatively, be constituted by a predetermined magnetic signal. It will also be assumed that information-bearing portion 3 is provided with a spiral signal information track; and that this spiral track is provided with recorded signal information in the form of irregular surface modulations, such as pits or grooves. Disc 1 thus may comprise a phonograph disc or a video disc. As an alternative, information-bearing portion 3 of disc 1 may be provided with magnetically recorded signal information in the form of a spiral track.
Referring now to FIGURE 2, a block diagram is shown comprised of apparatus for recording signal information on information-bearing portion 3 of disc 1. In the illustrated embodiment, disc 1 is to be used as the master disc from which multiple copies are stamped. Disc 1 is comprised of a base 5 upon which a metal film 6, such as aluminum or other light-reflective material, is deposited such as by evaporation.
It is appreciated that film 6 corresponds to circular track 4 shown in FIGURE 1. This circular track has a width of approximately 1 mm. and a thickness of about 0.1 ~m. A slit 7, such as illustrated in FIGURE 3A, is formed in the upper surface of film 6, this slit having a V-shaped groove, as illustrated, or any other suitable configuration to provide a circular discontinuity in the upper surface of the film. This slit has a width of approximately 4 ~m. As will be understood, if light is transmi-tted to impinge upon the upper surface of ; film 6, it will be reflected therefrom along a predetermined path except for that portion of the light that impinges slit 7.
This will be explained in greater detail below.
The top surface of base 5 is provided with a transformable layer 10 of uniform thickness. Disc 1, formed as aforedescribed, is placed upon a turntable 9 having a rotary shaft 8. This rotary shaft is adapted to be inserted into central bore 2 of 20 the disc. Suitable recording apparatus, enclosed within block B, deforms transformable layer 10 with a carrier modulated with signal information as disc 1 rotates. As will be ; described below, the transformable layer may be a photoresist which is exposed to a light beam modulated with signal information, thereby to form a latent image on the photoresist layer of the information to be recorded.
In the illustrated embodiment, recording apparatus B
is comprised of a transducer 22 adapted to scan the upper surface of disc 1 along a predetermined spiral track. To this effect, a suitable drive mechanism, not shown, displaces transducer 22 in a radially inward direction as disc 1 rotates about its axis formed of rotary shaft 8. Although the scanning movement _g_ ' 1~8SOSO
of transducer 22 is related to the rotary movement of disc 1, fluctuations in rotary shaft 8 will result in eccentric rotation of the disc to cause a lateral shift between a given point on the upper surface of the disc and the transducer.
This could result in the formation of an information track that deviates from the predetermined spiral track. In accordance with the apparatus now to be described, the formation ., of the spiral track by transducer 22 is compensated in the event of eccentric rotation of disc 1.
Apparatus enclosed within block A is adapted to sense v a lateral shift in disc 1 during its rotation. In accordance with illustrated embodiment, this apparatus is comprised of a light source 11, opti¢al elements 12, 15 and 16 to focus the light emitted from source 11 onto metal film 6 forming circular track 4, and optical elements 14, 15 and 17 to detect light reflected from the metal film and to sense a lateral shift of disc 8 as a function of a characteristic of the reflected light. Preferably, light source 11 is a He-Ne laser which emits a linearly polarized laser beam. This beam is transmitted to a beam-splitter 12 such that a portion of the emitted beam is transmitted through the beam-splitter to a light detector 13 and another portion of the emitted laser beam is reflected by beam-splitter 12 through a polarized beam-splitter 14, a quarter-wavelength plate 15 and a condenser lens 16. Polarized beam-splitter 14 is matched to the linear polarized direction of laser beam bl reflected from beam-splitter 12. Hence, substantially all of beam bl is transmitted through beam-splitter 14 to quarter wavelength plate 15. The quarter wavelength plate is conventional and is adapted to . 30 transmit a circular polarized beam in response to the linear ; polarized beam applied thereto by beam-splitter 14. Condenser lens 16 focuses beam bl onto metal film 6 in the vicinity of 1()8S(~S(~
slit 7. The focused beam spot produced by lens 16 is approximately 4 ~m.
As will be described, at least a portion of the focused beam is reflected from the surface of metal film 6 through lens 16 and through quarter wavelength plate 15. This reflected light beam is circularly polarized and, consequently, quarter wavelength plate 15 acts upon this circularly polarized beam to produce linear polarization thereof in a direction which is perpendicular to the linear polarization of beam bl that had been transmitted initially to plate 15. The direction of polarization of the reflected beam which now impinges upon beam-splitter 14 is blocked from being transmitted through this beam-splitter and, instead, now is reflected thereby to light detector 17. By properly selecting the polarizing directions of the transmitted and reflected light beams, the same optical elements 14, 15 and 16 can be used to transmit beam bl onto metal film 6 and to reflect the beam that is reflected from this metal film onto light detector 17. Thus, the light transmission and reflection paths traversed between beam- -splitter 14 and metal film 6 are coincident. In an alternative embodiment, separate light transmission and light reflection paths are used.
Light detector 17 is adapted to produce a control signal having a particular characteristic proportional to the intensity of the light beam reflected from metal film 6 and impinging thereon. In a preferred embodim~nt, the magnitude of the control signal is proportional to the intensity of light impinging upon light detector 17. With particular reference to FIGURES 3B-3D, the magnitude of the control signal produced by the light detector is a representation of the magnitude and direction of a lateral shift of disc 1 during its rotation.
' ~
~08SO~U
,, More particularly, let it be assumed that beam bl impinges upon metal film 6 in the vicinity of slit 7 thereon such that a portion bl' is reflected from the top surface of the metal film and another portion bl" impinges upon the slit proper and, consequently, is not reflected along the incident light path.
When disc 1 rotates properly, a predetermined portion bl' (FIGURE 3B~ is reflected from metal film 6. That is, the position of slit 7 during rotation of disc l relative to a fixed reference point, such as a reference point defined by optical elements 12, 14, 15 and 16 is a predetermined position.
~f disc 1 is shifted in a lateral direction, such as in a radially inward direction, slit 7 is displaced relative to the fixed reference point, as shown in FIGURE 3C. Consequently, a greater portion bl' of incident beam bl is reflected from metal film 6. Therefore, the reflected beam impinging upon light detector 17 has a greater intensity, resulting in a control signal of higher magnitude. Conversely, if disc l is laterally shifted in a radially outward direction such that slit 7 is displaced relative to the fixed reference point as shown in FIGURE 3D, substantially none of the incident light beam bl is reflected from metal film 6. Thus, the intensity of reflected light impinging upon light detector 17 is at a minimum, and the corresponding control signal magnitude also is a minimum value.
Variations in -the intensity of the control signal produced by light detector 17 as a function of a detected displacement in slit 7 relative to the fixed reference point, such as occurs during eccentric rotation of disc 1, is graph-ically depicted in FIGURE 4. When the distance between the center-point of slit 7 and the fixed reference point is equal to S, such as when disc 1 rotates properly as depicted in .. . .
~085050 .. .
FIGURE 3B, the magnitude of the control signal produced by light detector 17 is represented as the level T. When the center-point of slit 7 is shifted s-o as to coincide with the fixed reference po;nt, substantially no portion of the incident beam bl is reflected from metal film 6 (FIGURE 3D), resulting in a control signal whose magnitude is a minimum. It is appreciated that, during normal rotation of disc 1, a portion bl' of incident beam bl should be reflected so that the direction of displacement of the disc can be determined by sensing a decrease or increase in the intensity of the reflected beam.
To avoid variations in the control signal produced by light detector 17 as a function of a change in the intensity of the light beam emitted by laser 11, the control signal is "normalized" with respect to the emitted laser beam intensity.
Essentially, this is performed by a divider circuit 18 coupled to receive the control signal produced by light detector 17 and to divide the magnitude of this control signal with the magnitude of a detected output signal produced by light detector 13. In this manner, deviations in the control signal produced by light detector 17 attributed to variations in the intensity of the laser beam emitted by laser 11 are cancelled because such deviations also will appear in the detected output signal produced by light detector 13. This "normalized"
output signal produced by divider circuit 18 is amplified by a preamplifier 19 and supplied to the recording apparatus in block B for the purpose of adjusting the track along which transducer 22 scans so as to compensate for lateral shifts in disc l caused by eccentric rotation thereof.
In the embodiment of the recording apparatus included within block B, signal information is applied to an input ``- 108SOS0 terminal 24a to modulate a carrier, wElereby stylus 22 records the ïnformation-modulated carri`er onto disc 1. If transducer 22 comprises a stylus, the information-modulated carrier corresponds to mechanical vibration of the stylus as determined by the signal information. Thus, the stylus will cut a corresponding groove in the upper surface of disc 1 as the disc rotates and as the stylus scans the disc in, for example, a substantially spiral track. For the embodiment wherein disc 1 comprises a magnetic disc, the carrier is a suitable bias signal that is modulated with signal information, and transducer 22 comprises a conventional magnetic recording head.
In the illustrated embodiment under discussion, transducer 22 comprises an optical, or light-recording, head wherein the carrier is a light beam which is modulated by the signal information applied to input terminal 24a. This signal-modulated light suitably exposes photoresist layer 10 to form a latent image of the signal information, this image subsequently being developed and fixed in accordance with conventional techniques.
As shown in the illustrated embodiment, a suitable light source, such as an Ar laser 23 emits a laser beam which is transmitted to a conventional light modulator 24 whereat signal information applied to input terminal 24a modulates the laser beam carrier. The modulated laser beam b2 is reflected from a suitable reflecting surface, such as mirror 21, and is focused by a condenser lens 25 to form an information-modulated light spot onto the upper surface of photoresist layer 10 on disc 1. This information-modulated laser beam thus scans a substantially spiral track as transducer 22 moves in a generally radially inward direction while disc 1 rotates about its axis. As mentioned previously, in the event of a .
.
:
108S0~(~
radial dïsplacement of disc 1 during its rotation, resulting in eccentric rotation of the disc, the actual information track scanned across the surface of the disc by transducer 22 will vary from its ideal spiral track. Consequently, when information is reproduced from the record disc, or when the record disc is used to make multiple copïes from which information is reproduced, such deviations in the recorded information track will deleteriously affect the reproduced signals, particularly if the disc is not subjected to an a identical eccentric rotation during a signal reproducing operation.
This problem is substantially overcome by adjusting the formation of the signal information record track during recording by shifting the location at which the modulated laser beam impinges photoresist layer 10 of disc 1 in response to sensed eccentric rotation of the disc. This is achieved by ; applying the amplified control signal produced by preamplifer 19 through an additional amplifier 20 to a positioning device for mirror 21. As an example, mirror 21 may be mounted on a ; 20 D'Arsonval movement so that the path along which modulated laser beam b2 is directed is a function of the amplified control signal applied to the D'Arsonval coil. Thus, it may be appreciated that the combination of circular track 4 having metal film 6 and slit 7 therein, together with the sensing i apparatus including light detector 17, and adjustable mirrordevice 21 function as a servo system to maintain the ` information-modulated laser beam b2 at a proper location on ; the surface of disc 1 despite any radial displacement or eccentric rotation of the disc.
The servo control function of the illustrated apparatus will best be understood if it is assumed, in the interest of , .
108505~) simplification, that information-modulated laser beam b2 is adapted to scan a circular information track only. If disc 1 is displaced in a radially outward direction by an amount ~r, the intensity of light reflected to light detector 17 is reduced, as seen in FIGURE 3D. This shift ~r in disc 1 would deviate the circular track scanned by information-modulated beam b2 by a corresponding amount ~r. However, the detected change in light intensity, as sensed by light detector 17, applies a control signal to, for example, the D'Arsonval move-ment to which mirror 21 is mounted, thereby changing thereflecting path along which information-modulated beam b2 is transmitted, resulting in a displacement of the information beam spot on the surface of disc 1 by an amount ~r. Hence, even though disc 1 may be subjected to eccentric rotation, the information track scanned across the surface of the disc is substantially maintained at a correct distance from circular track 4 in accordance with a predetermined relation. Although the foregoing has assumed that this predetermined relation is a fixed distance, that is, the information track is a circular track, it now should be fully appreciated that the instantaneous distance between the point of incidence of information-modulated beam b2 from circular track 4 may vary in accordance with a predetermined function so as to scan a spiral information track across the surface of the disc.
` A similar control operation is performed to adjust the ;` point of incidence of information-modulated beam b2 on the ` surface of disc 1 in the event that the disc is subjected to a radially inward displacement by an amount ~r, such as depicted in FIGURE 3C. In the interest of brevity, description of this operation is not provided.
Once the signal information applied to input terminal ,::
- i~)850S0 24a is recorded in the form of a latent image on the surface of photoresist layer 10 of disc 1 in the manner descrïbed above, the disc can be removed from turntable 9 and developed and fixed in accordance with conventional techniques. This results in the formation of a surface irregularity in the form of pits or grooves corresponding to the light-exposed portions of the photoresist layer. Then, the surface of the photoresist layer, after developing and fixing, is plated with nickel, chromium, or other suitable material. Once plated, the record disc can be used as a master from which multiple copies are stamped.
; Alternatively, and as is conventional, the nickel- or chromium-plated record disc can be used to stamp a master disc from which the multiple copies are produced. In either manufacturing process, it is seen that the surface irregularities formed on ; the surface of disc 1 as a result of exposure of the photoresist layer 10 to information-modulated light will be produced in the copies thereof, these surface irregularities being detectable ; by a suitable transducer so as to reproduce the recorded signal information.
Although the foregoing has described a recording operation wherein disc 1 is provided with a surface layer of a photoresist which is exposed to information-modulated light, it is appreciated that the surface of disc 1 may be provided with a lay-er of other transformable material and a compatible carrier can be modulated to deform such material to form irregular surface undulations representing such information.
For example, the deformable material may be a thermoplastic material, and the carrier used therewith may be thermal energy that is modulated with information to be recorded. As another alternative, the transformable material may be an electrostatic-or electrophotostat;c-sensitive medium, and the carrier may )850S0 be an electric charge that ï.s modulated with. signal information to be recorded or may be an informati.on-modulated light beam adapted to selectively dïssipate a charge provided on the su.rface of such a medium.
Turning now to FIGURE 5, there is illustrated a preferred embodiment of signal reproducing apparatus capable of reproducing the si.gnal information that had been recorded on the information-bearing portion 3 of disc l ~y the apparatus depicted in FIGURE 2 and described above. Accordingly, disc 1 is provided with surface irregularities in the form of undula-. tions, such as pits or grooves, at information-bearing portion 3 and also is provided with a circular track having slit 7 therein. In use, disc l is placed upon a turntable 27 and a rotary shaft 26 is inserted into the central bore of the disc for rotating the record medium. Displacement of disc 1 in the radial direction, as during eccentric rotation, is sensed by the apparatus enclosed within ~lock A. This apparatus is substantially identical to that previously described in ;~ conjunction with FIGURE 2. Hence, in the interest of brevity, . 2Q duplicative explanation here is avoided. Suffice it to say that radial displacement of disc 1 is sensed by detecting the corresponding movement of slit 7 which, as described previously, affects the intensity of the light beam reflected from the circular track to light detector 17, as depicted in FIGURES
.` 3B-3D. Consequently, an amplified control signal is produced by preamplifier 19 having a magnitude proportional to the sensed radial displacement of disc 1.
It is understood that the signal information reproducing apparatus must be compatible wi.th the si.gnal recording apparatus described previously in conjunction with the embodiment shown in FIGURE 2. Accordingly, such signal information reproducing apparatus is adapted to sense the signal information recorded - 1 ~
' 1~8S050 as surface irregularities on disc 1 by transmitting a light beam, such as a laser beam, onto tfi.e surface of the disc and detecting modulations in the reflected light from the disc. To this effect, a light source, such as a He-Ne laser 28 emits a linearly-polarized laser beam that is transmïtted to a beam~spli.tter 29. Beam-splitter 29 is substantially similar to aforedescrib.ed beam-splitter 14 and is adapted to . transmit light therethrough having a linear polarization in a predetermined direction, but to reflect substantially all light that is transmitted thereto having a perpendicularly disposed lïnearly polarized direction.
The laser beam emitter by laser 28 passes through ;. beam-splitter 29 and through a quarter wavelength plate, this plate being substantially similar to aforedescribed quarter wavelength plate 15. Hence, quarter wavelength plate 30 changes . the polarization pattern of the emitted laser beam from a linear polarization to a circular polarization, as is conventional. This circularly polarized light is reflected from a mirror 21 along path b3 a~d is focused by a condenser lens 31 to a beam spot on the surface of disc 1. Light beam b3 impinging upon the surface irregularities of disc 1 is reflected from the disc to traverse the same light path through condenser lens 31 and mirror 21, now in the opposite direction.
This reflected light beam is modulated in accordance with the signal information recorded on disc 1, and is reflected by mirror 21 to pass through quarter wavelength plate 30. The circular polarization of this modulated beam is converted by . the quarter wavelength plate into a linear polarization which now is in a directïon substanti.ally perpendicular to the linearly polarized direction of the laser beam emitted from laser 28. Consequently, this information-modulated light lV8SOSO `
beam is substantially entirely reflected by beam splitter 29 to a lîght detector 32 whereat the modulated signal information is recovered.
For the embodiment wherein mirror 21 and condenser lens 31 comprise a transducer 33 adapted to scan a spiral track across the surface of information-~earing portion 3 of disc 1, a suitable drïve mechanism ~not shown~ is provided to advance the transducer in a radial direction as the disc rotates.
Similarly, if transducer 33 is adapted to scan concentric circular tracks across the surface of disc 1, a suitable driving mechanism is provided to advance the transducer in a radial direc~tion.
As in the previously described recording apparatus, in the event of a radial displacement of slit 7 in circular track 4 caused by eccentric rotation of disc 1, as by fluctuations in rotary shaft 26, the amplified control signal produced by preamplifier 19 and further amplified by amplifier 20 serves to vary the position of mirror 21 so as to correspondingly displace the point of incidence of beam b3 on the surface of disc 1 so as to compensate for such radial displacement. Hence, mirror 21 may be secured to a D'Arsonval movement such that the angular position of the mirror is adjusted as a function of the magnitude of the control signal. Thus, beam b3 impinges upon the surface of disc 1 at a location that is relatively fixed from slit 7 of circular track 4 in accordance with a predetermined relation. As is recognized, for the embodiment wherein signal information is recorded in a spiral track, this "predetermined relation" establishes a spiral scanning track of beam b3-It is appreciated that the control over the location at which beam b3 impinges upon the surface of disc 1 during a signal reproduction operation is substantially identical to the , ~
- ~850S0 : :.
control over beam b2 descri~ed previously with respect to a signal recording operation. Hence, further description of the reproducing apparatus shown in FIGURE 5 need not be described.
It should be recognized that the reproducing apparatus ; which is used to recover the previously recorded signal information should be compatible with the nature of disc 1.
For example, if d;sc 1 is a phonograph disc, transducer 33 is a suitable stylus. Alternatively, if disc 1 is a magnetic disc, transducer 33 is a conventional magnetic reproducing head.
1 10 In the for~going embodiments, it has been assumed that ; the reference information provided in circular track 4 is constituted by slit 7 disposed in a light-reflective material, such as metal film 6. As an alternative embodiment, this reference information may consist merely of a narrow light-, reflective track, such as a track whose width is about 4 ~m.
Still another embodiment of circular track 4 is illustrated in FIGURE 6 as comprising a first circular pattern 5A of uniformly spaced light-reflective elements having a first periodicity, and a second adjacent circular pattern 5B of uniformly spaced light-reflective elements having a second periodicity. Super-imposed on these adjacent circular patterns of light-reflective elements is beam spot 34 corresponding to the focused light beam bl. As is seen, a portion of beam spot 34 impinges upon circular pattern 5A and another portion of the beam spot impinges upon circular pattern 5B. Hence, the intensity of light reflected to light detector 17 includes a first component corresponding to the periodicity of light-reflective elements 5A and a second component corresponding to the periodicity of light-reflective elements 5B. In accordance with the illustrated embodiment shown in FIGURE 6, the first component of the light intensity is of a higher frequency than the second component thereof. When disc 1 rotates properly such that ~ -21-:
.
circular track 4 is located in proper relation with respect to the fixed reference point defined by beam spot 34, the f;rst, or higher frequency component of reflected light will exhibit a first predetermined intensity and the second, or lowe frequency component of the reflected light will exhibit a second predetermined intensi.ty. Any shift in the relative position of circular track 4 with respect to fixed beam spot 34, as by eccentric rotation of disc 1, will alter the respec-tive intensïties of the higher and lower frequency components of the light reflected to light detector 17. This change in .
the respective li.ght intensities is used to produce a control signal corresponding *o the direction and magnitude of a radial shift in disc 1. As before, th;s control signal is ::~-used to adjust the track scanned by transducer 22 or by transducer 33 so as to compensate for eccentric rotation of disc 1.
While the present invention has been particularly shown and described with reference to certain preferred embodiments -thereof, it should be readily apparent that various changes and modi.fications in form and details, such as those suggested hereinabove, as well as others, will be readily apparent to those of ordinary skill in the art. For example, the detectable pattern of indicia forming the reference information provided in circular track 4 may be a predetermined magnetically~
recorded signal, optically detectable indicia, and the like.
Also, recording transducer 22 as well as reproducing transducer 33 may- exhibit the various alternative embodiments described above, or may be differently constructed. For example, these respective transducers may generate an electron beam suitable 3Q for recording and detecting information on disc 1. Therefore, ; it is intended that the appended claims be interpreted as -22~
including all of the foregoin~ changes and modifications in structure snd in use of the aforedescri~ed invention.
.
.
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.:
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Claims (7)
1. A method of recording signal information on a rotatable record medium having a circular track thereon provided with a detectable predetermined pattern, comprising the steps of rotating said record medium about an axis which is at least approximately concentric with the center of said circular track thereof; recording said signal information on said record medium during rotation of the latter thereby to form an information track; continuously detecting only said predetermined pattern in said circular track during said rotation of said record medium to sense any eccentricity of said circular track in respect to said axis of rotation;
and adjusting the formation of said record track in response to sensed eccentricity in the rotation of said record medium to compensate for such eccentric rotation and thereby maintain a precisely predetermined relation of said information track to said circular track.
and adjusting the formation of said record track in response to sensed eccentricity in the rotation of said record medium to compensate for such eccentric rotation and thereby maintain a precisely predetermined relation of said information track to said circular track.
2. The method of Claim 1 wherein said step of detecting said predetermined pattern to sense eccentric rotation of said record medium comprises generating a control signal having a characteristic that varies as a function of the amount and direction of eccentric rotation of said record medium.
3. The method of Claim 2 wherein said step of adjusting the formation of said record track to compensate for said eccentric rotation comprises deviating said record track from a predetermined path in response to said control signal.
4. The method of Claim 2, wherein said predetermined pattern is a light reflective pattern and said control signal is generated by transmitting a light beam onto said light reflective pattern, reflecting said light beam from said pattern onto a light detector, and generating a control signal having a magnitude proportional to the intensity of the light beam impinging upon said light detector.
5. A method of recording signal information on a record disc of the type having a predetermined detectable pattern formed as a circular track on a surface of said disc and a layer of transformable material provided over substantially the entire remainder of said surface, comprising the steps of rotating said disc about an axis which is at least approximately concentric with the center of said circular track thereof;
modulating a carrier with signal information; exposing said transformable layer with the modulated carrier as said disc rotates to form an information track; continuously detecting only said predetermined pattern as said disc rotates to sense any eccentricity of said circular track in respect to said axis of rotation thereof; adjusting the formation of said record track by shifting the location at which said modulated carrier impinges on said transformable layer in response to sensed eccentricity of the rotation of said disc to compensate for said sensed eccentricity and thereby maintain a precisely predetermined relation of said information track to said circular track; and developing and fixing said exposed transformable layer on said surface of said record disc to form an irregular surface corresponding to said signal information.
modulating a carrier with signal information; exposing said transformable layer with the modulated carrier as said disc rotates to form an information track; continuously detecting only said predetermined pattern as said disc rotates to sense any eccentricity of said circular track in respect to said axis of rotation thereof; adjusting the formation of said record track by shifting the location at which said modulated carrier impinges on said transformable layer in response to sensed eccentricity of the rotation of said disc to compensate for said sensed eccentricity and thereby maintain a precisely predetermined relation of said information track to said circular track; and developing and fixing said exposed transformable layer on said surface of said record disc to form an irregular surface corresponding to said signal information.
6. The method of Claim 5, wherein said predetermined pattern is a light reflective pattern and is detected by transmitting a light beam from a fixed source to a predetermined location with respect to said pattern, reflecting said light beam from said pattern to a light detector, and generating a control signal proportional to the intensity of said light beam reflected to said light detector, said intensity varying from a predetermined level when said light beam impinges on said pattern at a location that varies from said predetermined location due to eccentric rotation of said disc.
7. The method of Claim 6, wherein said carrier is a second light beam and said deformable material is a photo-resist, and wherein the location at which said modulated carrier impinges said transformable layer is shifted by reflecting the modulated second light beam onto the photoresist layer along a predetermined path, and varying the reflecting path of said modulated second light beam as a function of said control signal.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP50157200A JPS5280007A (en) | 1975-12-26 | 1975-12-26 | Video disc |
| JP157200/75 | 1975-12-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1085050A true CA1085050A (en) | 1980-09-02 |
Family
ID=15644380
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA268,574A Expired CA1085050A (en) | 1975-12-26 | 1976-12-22 | Method for recording information on a rotatable medium |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5280007A (en) |
| CA (1) | CA1085050A (en) |
| DE (1) | DE2658677A1 (en) |
| FR (1) | FR2336766A1 (en) |
| GB (1) | GB1565829A (en) |
| NL (1) | NL7614450A (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4074085A (en) * | 1976-03-31 | 1978-02-14 | Eli S. Jacobs | Multiple beam optical record playback apparatus for simultaneous scan of plural data tracks |
| DE3066828D1 (en) * | 1979-07-16 | 1984-04-12 | Discovision Ass | Video player/recorder for recording on a blank disk and method for home recording |
| JPS57130240A (en) * | 1981-02-05 | 1982-08-12 | Olympus Optical Co Ltd | Optical information recording and reproducing device and information recording medium for it |
| US4424539A (en) * | 1981-12-23 | 1984-01-03 | International Business Machines Corporation | Magnetic disk-control track read through envelope |
| GB2188474A (en) * | 1986-03-27 | 1987-09-30 | Philips Electronic Associated | Electronic digital storage apparatus |
| GB8624444D0 (en) * | 1986-10-11 | 1986-11-12 | London Weekend Television Ltd | Optical disc |
| JPH04305821A (en) * | 1991-04-02 | 1992-10-28 | Sony Corp | Disk reproducing device |
| JP3063230B2 (en) * | 1991-05-31 | 2000-07-12 | ソニー株式会社 | Rewritable disk and disk device |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1183948B (en) * | 1961-01-12 | 1964-12-23 | Telefunken Patent | Memories, especially micro memories for information |
| US3361873A (en) * | 1962-05-07 | 1968-01-02 | Minnesota Mining & Mfg | Disc recording system |
| US3479664A (en) * | 1965-12-28 | 1969-11-18 | Data Products Corp | Servo positioning system |
| NL174591C (en) * | 1973-02-09 | 1984-07-02 | Philips Nv | DISC REGISTRATION CARRIER BODY. |
| DE2453364C3 (en) * | 1973-11-09 | 1979-02-22 | Hitachi, Ltd., Tokio | Automatic focusing device |
| US3881184A (en) * | 1974-05-28 | 1975-04-29 | Ibm | Adaptive digital servo system |
| FR2315142A1 (en) * | 1975-06-17 | 1977-01-14 | Pyral Soc | Transducer head guide system - using additional guide track associated with magnetic recording track |
-
1975
- 1975-12-26 JP JP50157200A patent/JPS5280007A/en active Pending
-
1976
- 1976-12-09 GB GB51505/76A patent/GB1565829A/en not_active Expired
- 1976-12-22 CA CA268,574A patent/CA1085050A/en not_active Expired
- 1976-12-23 DE DE19762658677 patent/DE2658677A1/en not_active Ceased
- 1976-12-24 FR FR7639100A patent/FR2336766A1/en active Granted
- 1976-12-27 NL NL7614450A patent/NL7614450A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| NL7614450A (en) | 1977-06-28 |
| DE2658677A1 (en) | 1977-07-14 |
| GB1565829A (en) | 1980-04-23 |
| JPS5280007A (en) | 1977-07-05 |
| FR2336766A1 (en) | 1977-07-22 |
| FR2336766B1 (en) | 1984-09-14 |
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