Note: Descriptions are shown in the official language in which they were submitted.
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The subject matter of the present invention
relates generally to multiple layer optical data records
and associated playback apparatus, and in particular to such
records which include a plurality of data information tracks
in different data layers provided on at least one side of
the record substrate or base member, and to such playback
apparatus which includes selection means for selectively
reading out one of such data tracks with a scanning light
beam to produce an electrical readout signal corresponding
to the data on the scanned track. The multi-layered records
and playback apparatus of the present invention are
extremely useful for high density information storage. For
example, one application of the present invention is the
recording and playing back of audio and video signals used
in television programs.
Previously it has been suggested in U. S. Patent
3,430,966 of D. P. Gregg, granted March 4, 1969, and U. S.
Patent 3,518,442 of K. O. Johnson, granted June 30, 1970, to
provide an optical data record in which data is recorded by
notches in two tracks on opposite sides of a light trans-
missive substrate member. However, such prior art records
and their associated playback apparatus have several
disadvantages since ~he records oniy have one data layer
per side and are read out by transmitting a light beam
through the record including a light diffusing layer
provided between the two data layers. As a result, these
records cannot store as much data as the record of the
present invention and are more expensive and difficult to
manufacture. Also, the playback apparatus requires separate
focusing optical systems for the light detector and for the
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light source because they are on opposite sides of the
record. Thus, the playback apparatus is not as compact as
the embodiment of the present invention employing reflective
records because in the latter the detector is positioned on
the same side of the record as the light source.
It has been proposed by K. Compaan and P. Kramer
in Philips Technical Review, Volume 33, pages 178 to 180,
1973 No. 7, to employ light reflecting optical data records
so that the detector and light source may be positioned on
the same side of the record and may use common optical
elements. However, this record has the disadvantage that
optical data is recorded as pits or notches in a single
layer which is formed in a conventional manner by pressing
the records from a master. As a result, only about thirty
minutes of television programs can be recorded on a large
record of 30 centimeters in diameter, the size of a
conventional long playing phonograph record. The entire
surface of the record, including the data pits, is coated
with metal for reflecting the light beam so that several
data layers could not be recorded on the same side of the
record in the manner of the present invention. The data
pits, unlike the background surface, reflect the light beam
away from the detector and are detected by the absence of
light at the detector so that there is a lower signal to
noise ratio in the electrical readout signal than that of
the present invention.
Also of interest as a background on optical data
records and playback systems for fixed records in U. S.
patent 3,501,586, granted March 17, 1970, to J. T. Russell.
However, this patent does not disclose multi-layered data
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records in the manner of the present invention.
It is, therefore, one object of the present
invention to provide an improved optical data record of
higher storage density having a plurality of data tracks
recorded in different data layers on at least one side of
the record substrate.
Another object of the invention is to provide such
a multi-layered data record of simple and economical con-
struction which is provided with optical data tracks of high
accuracy without forming pits or grooves in the record
surface.
A further object of the invention is to provide
such a multi-layered data record of light reflective
material so that it may be played back by using a light
source and detector positioned on the same side of the
record and using at least some of the same optical elements
to provide a more compact and less expensive playback
apparatus.
Still another object of the present invention is
to provide such a record in which the light reflected from
the data spots is detected to produce an electrical readout
signal of high signal to noise ratio.
An additional object of the present invention is
to provide an improved playback apparatus including a
selection means for selectively playing back the data tracks
on different data layers provided on such a multi-layered
data record.
Another object of the invention is to provide such
a playback apparatus which selects the data tracks to be
played back by changing the focus of the readout light beam
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from one track to another in a simple, accurate manner.
A still further object of the present invention is to
provide such an improved playback apparatus and record in which
the data tracks are selectively played back by providing the
data layers with different optical properties and detecting
only light with the optical property of the selected data track.
According to one aspect of the invention there is
provided a multi-layered optical data record comprising: a
base member including a first side and a second side separated
by the thickness of said base member; a plurality of optical
data layers having optical data information spots recorded
thereon, including first and second data layers of different
data provided on the same side of said first and second sides
of said base member; said first and second data layers being
contiguous so that corresponding surfaces of said layers are
separated by a distance less than the thickness of said base
member; and said first and second data layers each having
complete data recorded thereon so that only one data layer at a
time is used to modulate the readout light and thereby produce
a readout signal of the data in said one layer.
According to another aspect of the invention there is
provided a record playback apparatus for optical data records
comprising: light source means for generating at least one light
beam; support means for supporting a multi-layered optical data
record having optical data information spots recorded in tracks
on different layers of said record, said record including a base
member and a plurality of optical data layers recorded thereon
including first and second data layers of different data provided
on the same side of said base member; focusing means for focusing
at least one light beam on the track of a data layer on said
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record to substantially the same size as the width of a data
track: scanning means for scanning said data tracks with said
light beam including means for providing relative movement between
the light beam and record to cause said scanning; readout means
for transmitting a readout portion of the scanned light beam
from said record to at least one light detector means to cause
said detector means to produce an electrical readout signal
corresponding to the data on the track being scanned; and
selection means for selectively reading out one of the data
tracks of the plurality of data layers provided on one side of
the record to cause the selected data track of one layer to
produce the readout signal.
Other objects and advantages of the present invention
will be apparent from the following detailed description of
the preferred embodiments thereof and from the attached drawings
of which:
Fig. 1 is a schematic diagram of one embodiment of
a playback apparatus for a reflective type of multi-layer optical
data record in accordance with the present invention;
Fig. 2 is an elevation view taken along the line 2-2
of Fig. l;
Fig. 3 is a schematic diagram of a second embodiment of
a playback apparatus similar to that of Fig. 1 but modified for
light transmissive type multi-layer optical data records;
Fig. 3A is an elevation view taken along the line 3A-3A
of Fig. 3.
Fig. 4 is an enlarged section view of a portion of a
multi-layer optical data record with spacer layers between the
data layers which may be used in the playback apparatus of
Figs. 1 or 3;
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Fig. 5 is an enlarged section view of a portion of
another embodiment of the multi-layer optical da.a record of the
present invention with a reflection layer separate from the
data layers;
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Fig. 6 is an enlarged section view of a portion
of a third embodiment of a multi-layer optical data record
without spacer layers; and
Fig. 7 is an enlarged section view of a portion of
a fourth embodiment of the multi-layer optical data record
without spacer layers.
As shown in Figs. 1 and 2, a multi-layered optical
data record 10 of the reflective type, such as that shown in
Fig. 4 which employs light reflecting material for the data
spots or for the background regions surrounding transparent
data spots, is played back with a playback apparatus
including a light source 12 and a light detector 14 position-
ed on the same side of the record. This reflective playback
apparatus has the advantages of providing a more compact
apparatus and enabling the use of at least some of the
optical elements including the objective lenses 16 in the
same light paths for the light reflected from the record 10
to the detector 14 and for the light transmitted from source
12 to the record. This reduces the cost and causes some
of the defects of the optical system, such as lens aberra-
tion, to be cancelled as a result of the light beam travers-
ing the elements twice in opposite directions.
The light source 12 may be a laser which produces
"coherent" light of one or more narrow frequency bands, or
a suitable source of intense noncoherent l'white" light of
many frequencies, including ultraviolet light, infrared
light, as well as visible light. A light beam 18 is trans-
mitted from source 12 through a primary lens 20 and an
apertured light mask commonly referred to as a "pin hole"
element 22. Lens 20 focus the light beam to a small spot
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at the circular aperture of the pin hole element so that
such aperture shapes the light spot and forms the object
that is imaged onto the record by the objective lenses 16.
The light beam 18 is transmitted through a beam splitting
mirror 24 onto a rotating distributor mirror member 26 whose
outer surface is in the form of a five-sided polygon having
five mirrors provided thereon which correspond to five
objective lenses 16 which are carried on a rotating scanner
wheel 28. The distributor mirror member 26 is mounted on
the shaft 30 of the scanner wheel 28 so that it is rotated
with such wheel at a constant speed by an electrical motor
32 coupled thereto. As a result, the distributor mirror
member 24 rotates at the same speed as the objective lenses
16 so that one of the mirrors of such distributor member is
always aligned with its associated objective lens. Thus,
the distributor mirror member 26 distributes the light beam
to the objective lenses 16 one at a time as such lenses
rotate across the record 10 to playback one of the data
track lines 35 on such record as shown in Fig. 2.
The light beam 18 is reflected from one of the
distributor mirrors onto one of five objective mirrors 34
mounted on the scanner wheel 28 immediately beneath each
objective lens 16. As a result, the light beam is reflected
from the objective mirror 34 through its associated objective
lens 16 onto the multi-layer optical data record 10. The
light beam is focused by lenses 20 and 16 to a small spot
in a focus plane on one of the data layers of the record,
such spot being of a diameter which is substantially the
same size as the width of one of the data track lines 35 of
data spots provided on such record.
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A selection means is provided for moving the focus
plane from one data layer to another to selectively play back
the selected data track on such layers. This change in the
focus plane may be accomplished by moving the pin hole light
mask 22 and the primary lens 20 longitudinally along the
beam axis by means of an electromagnetic coil 36 and
associated electrical control circuit. The coil 36 attracts
or repels a magnetic armature 38 on which the pin hole mask
22 is mounted so that it and the lens 20 coupled thereto
move toward and away from the record 10. A spring biasing
element 40 may be used for mounting the pin hole light mask
22 which resists the electromagnetic force of the coil 36
for more accurate adjustment of the mask. However, it should
be noted that in view of the great distance of the light mask
22 from the record 10, the motion of the object formed by
the pin hole in mask 22 relative to the motion of the light
spot image in the focus plane is equal to the square of the
magnification which is approximately 10. Therefore, the
mask 22 must move about 100 times farther than the resulting
movement of the focus plane of the light spot on the record.
This enables accurate adjustment of the focus plane which is
required for selective playback of one of the data layers
in view of the extremely small distances between data layers.
The light spot focused on the record is scanned
along one line 35 of the data track without overlapping
adjacent track lines. This scanning in a longitudinal or
"X" direction along the track lines is accomplished by
rotation of the scanner wheel 28 at a speed of about 2500
RPM for a four and one-half inch radius to the center of the
objective lenses. To scan from line to line in the trans-
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verse or "Y" direction, the data record 10 is moved slowly
downward in the direction of arrow 41 in any suitable
manner, such as by a worm gear apparatus 42 which moves a
carriage 44 supporting the record and is suitably geared to
the motor 32. The speed of longitudinal movement of the
record 10 is about 420 microns per second for playing back
a television signal on a record five inches wide. As a
result, each objective lens 16 scans a separate data track
line 35 of the data track on one data layer of the record
10 as the scanner wheel 28 is rotated in the direction of
arrow 43.
The scanning light beam 18 is reflected from the
data spots or the surrounding background as a modulated
readout light beam back through the objective lens 16 to
the objective mirror 34 and distributor mirror 26 to the
beam splitter mirror. The beam splitter mirror 24 reflects
the modulated readout light beam 46 to the detector 14 which
is a photoelectric cell that produces an electrical output
signal corresponding to the modulated light beam. This
electrical readout signal is transmitted to the video input
of the television receiver or other utilization device
connected to the output of the detector through a suitable
amplifier and decoder system (not shown).
A "tipping" plate 45 which laterally displaces
the light beam 18 by refraction of such beam is provided
between the pin hole mask 22 and the beam splitter mirror
24. The tipping plate is pivoted by a galvonometer type
motor 47 in response to a tracking signal applied to its
input for changing the magnitude and direction of the lateral
displacement of the light beam 18 in order to cause such
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beam to stay on the data track being scanned. The tracking
signal is produced by a servo system connected to the output of
the detector 14 as is shown in United States patent application
Serial No. 483,131, filed June 26, 1974, by R. A. Walker, now
United States Patent 3,919,697, issued November 11, 1975.
It should be noted that the light beam 18 is not coaxial
with the distributor shaft 30 but strikes the distributor
mirrors 26 at a slight back angle which is less than the angle
between the reflecting surfaces of such mirrors and the shaft
axis. As a result the reflected light beam rotates at a speed
slightly less than that of shaft 30 and fully illuminates the
objective lenses with a substantially uniform intensity over
the entire data line 35. This is necessary because if the light
beam is parallel to the shaft axis when it strikes the dis-
tributor mirrors 26, the reflected beam will rotate at the same
speed as the objective lenses. This would cause the objective
lenses to be illuminated with only about one-half the beam
intensity at their switching positions where the beam is trans-
ferred from one lens to another by the distributor.
As shown in Figure 4, one embodiment of the multi-
layer optical data record 10 includes a record substrate
or base member 48 of a suitable plastic material, glass,
ceramic or metal, which may be light opaque for reflective
type records or light transparent for light transmission
type records. A plurality of data layers 5QA, 50B, SQC and
50D are provided on one or both sides of the substrate
member 48. The data layers are separated by transparent
plastic spacer layers 52 which may be made of the same
material as the substrate member 48. Each of the data layers
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has a series track or parallel tracks of data spots 54
formed by spaced track lines 35 on the record, as shown in
Fig. ~. The data spots are separated by spaces and may
represent binary coded digital information or frequency
modulated or pulse width modulated analog information.
The data layers 50A to 50D may be made of photosen-
sitive material, such as photographic film, in which case
the spacer layers are provided as the film backing. However,
the data layers may also be made by other suitable recording
material including printing ink, in which case the data spots
54 could be made of light opaque black material and the back-
ground made of transparent material for llght transmissive
type records. However, the data spots 54 may also be made
of light reflecting metal material formed by vapor deposition
through a mask having apertures corresponding to the data
spots, or by etching through a photoresist mask formed by
exposure to a light image of the data spots in a conventional
manner such as is used to form etched electrical circuit
boards. The thickness of the spacer layers 52 is greater
than the depth of focus of the objective lenses 16 so that
when the light beam 18 is focused on one of the data layers,
the remaining data layers are out of focus and do not block
the light beam appreciably, as shown in Fig. 4. A protective
layer 56 of transparent plastic is provided over the outer-
most data layer 50A to provide protection against mechanical
abrasion of the data layers and to prevent the dust which
settles on the surface of the record from blocking light to
the data layers, by spacing the dust from such data layers.
Thus, any dust which collects on the outer surface of the
protective layer 56 is out of focus with respect to the
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light spot focused on any of the data layers. For this
reason, the protective coating 56 may have a coating of about
10 mils while the spacer layers 52 may have a thickness of
about 5 mils and the substrate base member 48 has a thickness
of about 1/8 inch, depending upon the material used for
such substrate.
When the record of Fig. 4 is of a light transmissive
type record, the data spots 54 are preferably made of light
opaque material, while the surrounding background areas of
the data layers are made of light transparent material, as
is the record substrate 48. This light transmissive type
record may be played back by modifying the playback
apparatus of Fig. 1, as shown in Fig. 3. Thus, the light
detector 14 is moved to the opposite side of the record 10
from the light source 12 and aligned with the light beam
transmitted through the record 10 by the objective lens 16.
An arcuate lens segment 58 is positioned between the
detector 14 and the record, such lens segment having a
short focal length on the order of six inches and a field of
view which covers the entire width of the record element 10,
as shown in Fig. 3A, so that such lens may be held in a
fixed position during scanning. The arcuate lens segment 58
is cut from a large circular lens shown by dashed lines 59
in Fig. 3A. It should be noted that the beam splitting
mirror 24 is eliminated in the embodiment of Fig. 3.
While the selection means including coil 36 and
its control circuit 37 may be employed to change the focus
of the light beam 18 onto different data layers in the play-
back apparatus of Fig. 3 just as in the embodiment of Fig. 1,
another selection means consisting of a plurality of
different colored filters 60 and 62 equal in number to the
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data layers is shown in Fig. 3- In this case, the light
source 12 is not a laser, but a suitable source of intense
"white" light of many frequencies, and the record element
10 includes data layers of different optical properties,
such as different colored dyes or different colored photo-
luminescent materials, as shown by record 10' in Fig. 6.
The record 10' of Fig. 6 includes data layers 64A,
64B and 64C which are directly layered on each other without
the use of spacer layers, similar to layers 52 of Fig. 4,
between such data layers. This is possible because selection
of the data layers is not accomplished by changing the focus
plane, but by the color filters 60 and 62 in the selection
means shown in Fig. 3. As stated earlier, the data layers
64A, 64B and 64C are of different optical properties. Thus
the data spots in the three data layers may be made of
different colored dyes including the subtractive wave-
length dyes used in color photographic film or of different
light emission wavelength photoluminescent materials in
plastic binder layers. The data layers 64A, 64B and 64C
are of extremely small thickness on the order of .1 mil or
less, since they are all within the same field of focus of
the light beam.
The filters 60 and 62 equal in number to the data
layers are selectively positioned in front of the detector
14 by an electric motor 66 which may be a step motor
controlled by a suitable control circuit 68 for properly
indexing the filters which are carried on a rotating support
plate 70 attached to the motor shaft 72. The filters can
be of the additive or band pass type which transmit light
of the wave lengths blocked by the colored data spots in the
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data layers which are formed of subtractive or band reject
color dyes. The data spots of different colored dyes can
be formed by multiple exposure and development of color
photographic film with different colored light beams so
that the data layers are provided by the different emulsion
layers of such film. However, the data spots of different
photoluminescent materials may also be formed by printing
or by photoresist etching techniques in a similar manner
to the data spots of the record of Fig. 4. Also, the record
10' of Fig. 6 can be made as a reflective type record and
used in the playback apparatus of Fig. 1 if a reflective
layer is provided between the substrate 48 and the bottom
data layer 64C in a similar manner to Fig. S.
The record 10'' of Fig. 5 is a reflective type
record similar to that of Fig. 4, except that the data bits
54 are made of light opaque material, and a light reflecting
metal layer 74 is provided between the substrate 48 and a
spacer layer 52 beneath the bottom data layer. Thus, the
record 10'' of Fig. 5 is a reflective type record even
though neither the data bits 54 nor the surrounding back-
ground material of the data layers is of light reflecting
material. Of course, the reflecting layer 74 can be
provided by the surface of the substrate if such substrate
is made of metal, rather than plastic, which may be preferred
for dimensional stability.
A fourth embodiment of the multi-layered optical
data record 10''' is shown in Fig. 7 to be of the direct
layered type like that of Fig. 6, which does not use spacer
layers between its data layers 76A, 76B and 76C, but is
formed differently than the embodiment of Fig. 6. Thus,
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the data layers 76A, 76B and 76C in the record of Fig. 7
may be formed by evaporating the different colored dyes or
photoluminescent material of the data spots through a mask,
by mechanical printing or by using a photoresist etching
process. The lower data layer 76C is applied to the surface
of the substrate first, then the data layer 76B and finally
the upper data. For this reason, the data layer 76B contacts
layer 76C and the surface of the substrate through holes in
layer 76C in some places, while layer 76A contacts the
substrate and both the other layers 76B and 76C. These
data layers are formed of materials of different optical
properties similar to that of record 10' of Fig. 6, including
subtractive color dyes or photoluminescent materials which
emit different colored light when struck by the readout light
beam.
Selective readout of the data layers in the records
of Figs. 6 and 7 may be accomplished simultaneously by using
a plurality of detectors and associated filters and providing
beam splitting mirrors in a similar manner to that disclosed
in United States Patent 3,891,794, issued June 24, 1975,
by J. T. Russell. On those records in which the data spots
are transparent and the surrounding background areas are
opaque or reflective, it will be necessary to make the
background areas partially transparent, for example
approximately 50% transparent, so that sufficient light can
reach the lower data layer to enable playback.
The data layers 50 and spacer layers 52 of Figs.
4 and 5 can be formed in separate sheets and glued together
and to the substrate member by a suitable solvent for the
plastic material. However, photographic film strips exposed
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with different data tracks and developed may be used as
both the data layers and the spacer layers since the latter
are formed by the transparent film backing layers. The film
strips are transmitted through a tank of glue or solvent and
then attached to the substrate member and passed through
pressure rollers prior to drying. It should be noted that
color slide photographic film has a plurality of different
color emulsion layers which can be used directly as the
data layers to form a record like that of Fig. 6, since
chemical development and processing can be carried out
through the upper layers. However, in this case, there
would be multiple exposures of the film to different colored
light beams to form the data tracks on the different data
layers. Finally, it should be noted that for records using
photoluminescent material of different light emission
properties to distinguish between the data layers, the
playback light beam may preferably be of ultraviolet light
since most conventional photoluminescent materials are more
sensitive to ultraviolet.
It will be obvious to those having ordinary skill
in the art that many changes may be made in the details of
the above-described preferred embGdiments of the invention
without departing from the basis of the invention. There-
fore, the scope of the present invention should only be
determined by the following claims.
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