U.S. patent number 3,829,605 [Application Number 05/273,645] was granted by the patent office on 1974-08-13 for carrier and method for recording a signal thereon.
This patent grant is currently assigned to Ted Beldplatten Aktiengesellschaft. Invention is credited to Gerhard Dickopp.
United States Patent |
3,829,605 |
Dickopp |
August 13, 1974 |
CARRIER AND METHOD FOR RECORDING A SIGNAL THEREON
Abstract
An improved recording carrier of the type wherein the signals
are recorded in the form of depressable raised portions of the
surface thereof which are played back by means of pressure scanning
and which has a signal recorded thereon which results in variable
heights for the raised portions along the scanning path
corresponding to an envelope function of the recorded signal. The
raised portions are such that the distances of the base planes
thereof from a reference plane disposed perpendicular to the extent
of the heights of the raised portions along the scanning path vary
according to one of the envelope functions of the recorded signal
while the peaks of the raised portions lie substantially in a
single peak plane which is parallel to the reference plane. A
number of alternative methods for modifying the signal to be
recorded so as to produce the desired record are also
disclosed.
Inventors: |
Dickopp; Gerhard (Berlin,
DT) |
Assignee: |
Ted Beldplatten
Aktiengesellschaft (Zug, CH)
|
Family
ID: |
25761476 |
Appl.
No.: |
05/273,645 |
Filed: |
July 20, 1972 |
Foreign Application Priority Data
|
|
|
|
|
Jul 20, 1971 [DT] |
|
|
2136897 |
Jul 20, 1971 [DT] |
|
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7128351 |
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Current U.S.
Class: |
386/276; 369/61;
369/130; 386/312; 386/309; 386/304; 386/E5.068; 386/E9.011;
386/E9.001 |
Current CPC
Class: |
H04N
9/79 (20130101); H04N 5/7605 (20130101); H04N
9/80 (20130101) |
Current International
Class: |
H04N
9/80 (20060101); H04N 5/76 (20060101); H04N
9/79 (20060101); H04n 009/02 () |
Field of
Search: |
;178/6.6A,5.4CD
;179/1.41P |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Murray; Richard
Attorney, Agent or Firm: Spencer & Kaye
Claims
I claim:
1. In a recording carrier of the type wherein the signals are
recorded in the form of depressable raised portions of the surface
thereof which are played back by means of pressure scanning, said
record having a signal recorded thereon which results in variable
heights for said raised portions along the scanning path according
to an envelope function of the recorded signal, the improvement
wherein: the distances of the base planes of said raised portions
from a reference plane disposed perpendicular to the extent of the
heights of said raised portions along said scanning path vary
according to one of the envelope functions of the signal, and the
peaks of said raised portions lie substantially in a single peak
plane which is parallel to said reference plane.
2. In a method of recording a modulated carrier signal, whose
positive and negative maximum amplitudes along the time axis vary
in size according to similar envelope functions, on a record
carrier of the type wherein the signals are recorded in the form of
depressable raised portions of the surface thereof which are played
back by pressure scanning and with the heights of the raised
portions along the recording path varying according to the envelope
function, the improvement comprising the steps of:
modifying said carrier signal prior to recording so that all of the
maximum amplitudes in one of the oscillation directions are
substantially equal in amplitude, and thereafter recording the
modified carrier signal on the carrier in such a direction that the
maximum amplitudes of the same amplitude result in the peaks of the
raised portions of the carrier containing the recorded signal
whereby the peaks of the raised portions will lie substantially in
a single peak plane which is parallel to a reference plane disposed
perpendicular to the extent of the heights of the raised portions
along the direction used for scanning same and the distances of the
base planes of the raised portions from said reference plane will
vary according to one of said envelope functions.
3. A method as defined in claim 2 wherein said envelope functions
are approximately parallel to one another and are formed by the
superposition of a high frequency modulated carrier and a low
frequency modulated carrier, and wherein said step of modifying
comprises detecting said high and low frequency modulated carriers
in said carrier signal; amplitude modulating the detected high
frequency carrier with a signal corresponding to one of said
envelope functions; and superimposing said low frequency carrier on
the signal produced by said step of amplitude modulating.
4. A method as defined in claim 3 wherein said signal corresponding
to one of said envelope functions is in phase with said one of said
envelope functions.
5. A method as defined in claim 3 wherein said signal corresponding
to one of said envelope functions is of the opposite phase to said
one of said envelope functions.
6. A method as defined in claim 2 wherein said envelope functions
are approximately mirror images of each other with respect to the
time axis of the carrier signal and wherein said step of modifying
comprises superimposing a signal whose amplitude path follows one
of said envelope functions and has substantially the same amplitude
as one of said envelope functions on said modulated carrier
signal.
7. A method as defined in claim 6 wherein said signal which is
superimposed on said modulated carrier signal has the same phase as
said one of said envelope functions.
8. A method as defined in claim 6 wherein said signal which is
superimposed on said modulated carrier signal is of the opposite
phase to said one of said envelope functions.
9. A method as defined in claim 2 wherein said envelope functions
are approximately mirror images of each other with respect to the
time axis of the carrier signal; and wherein said step of modifying
comprises rectifying said modulated carrier signal.
10. A method as defined in claim 2 wherein said envelope functions
are approximately mirror images of each other with respect to the
time axis of the carrier signal; and wherein said step of modifying
comprises clamping the amplitudes of said carrier signal in one
direction at a constant level.
11. A method as defined in claim 2 wherein said modified carrier
signal includes a first carrier signal which is frequency or phase
modulated with the video luminance signal of a television
transmission signal and a superimposed second carrier signal of a
carrier frequency which is lower than the frequency of said first
carrier signal and which is modulated with the associated video
chrominance signal.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a recording carrier for the
storage of signals by means of depressable raised portions of its
surface for the purpose of pressure scanning and to a method of
recording signals on such record carriers. The term pressure
scanning is understood to mean a method for playing back stored
signals by means of a recording carrier whose surface is provided
with undulations or deformations corresponding to the time sequence
of the signal amplitude values and from which these signal values
are reproduced by means of a pickup which with its contact surface
exerts a pressure force on the carrier surface as the carrier is
moved relative thereto so that with the given modulus of elasticity
of the carrier material employed, the change in shape of the
carrier surface effected by the pressure force is substantially
greater than the oppositely directed deflection of the contact
surface of the pickup as a result of the compression.
Such a pressure scanning method is generally already known from
applicants U.S Pat. No. 3,652,809 issued Mar. 28th, 1972, and from
a publication by ALLGEMEINE ELECTRICITAETS-GESELLSCHAFT
AEG-TELEFUNKEN and TELDEC Telefunken-Decca-Schallplatten GmbH
bearing the title "Weltpremier Bildplatte Berlin 1970": [World
Premier Picture Record, Berlin, 1970] which was published in June,
1970 and a further publication which appeared in the magazine
"Funktechnik" Issue 14, 1970, pages 511-516. The above mentioned
patent with its teaching to scan a recording carrier with a
substantially soft body which resiliently yields under the pressure
of the pickup having a high deflection hardness, constituted a
contradiction of the previously valid view in the art that, in
order to have as wide as possible an expansion of the upper
frequence limit of the reproduction band, the recording carrier
must be as hard as possible and the pickup as resiliently soft as
possible. A suitable example for the unsuccessful conventional view
regarding an expansion of the reproduction range toward higher
frequencies is the publication "Factors Affecting the Stylus-Groove
Relationship in Phonograph Playback Systems" by G. R. Bastiaans
JOURNAL OF THE AUDIO ENGINEERING SOCIETY, Oct. 1967, Volume 15, No.
4, pages 389-399, since it contains a detailed explanation of the
theory of the relationships and gives values for the attainable
upper frequency limits for the type of phonograph playback systems
then in use.
In the above-mentioned patent a pickup, whose skid-shaped portion,
which is in engagement with the surface of the recording carrier
and performs only a very slight movement in amplitude while the
undulations on the surface of the recording carrier which contain
the signal experience substantially stronger compressions, made
available a further contiguous frequency range up to a few MHz
beyond the upper limit frequencies of the frequency range
utilizable with conventional disc recording means. The extension of
this upper frequency limit, which had heretofore been considered to
be unexceedable, means that now a good, usuable recording and
playback possibility is available for practical application. Such a
system provides the possibility of recording and playing back a
broadband signal which may serve, for example, for recording and
playing back a television broadcast with accompanying sound or for
recording and playing back a plurality of audio channels. As
previously mentioned, a skid-type pickup is used for this purpose.
This skid-type pickup has a leading end which slowly approaches the
surface of the recording carrier, so that the undulations on the
record carrier "creep" into the contact range at the leading end
during playback and a trailing end which has a relatively sharp
edge where the undulations quickly leave the contact range of the
pickup during playback.
In the process according to the above-mentioned patent, a plurality
of narrow band signals can be stored in the known multichannel
technique corresponding to the broad continuous operating frequency
band with an upper limit frequency of several MHz, or a broadband
signal, for example, a video signal, can be recorded and played
back which occupies the entire available frequency range. In the
latter case the requirement might arise for the accommodation of
one or more further signals, e.g., an audio signal or a color
information, in the same recording.
The principle of pressure scanning a frequency modulated carrier
wave which was basically outlined seems initially to be unsuited
for superposition of an additional signal oscillation or modulated
carrier wave because such a superposition would eliminate the
advantage of identical heights of the recorded oscillations to be
scanned. It can be seen that two superimposed recorded signals
would result in an oscillation with different height levels for the
peaks of the raised portions. The skid-type pickup possibly could
therefore no longer cover the raised portions of lower amplitude
which lie in the dales of the envelope of the resulting curve.
A solution for this problem has already been proposed in the
copending U.S. application of Thuy et al, Ser. No. 155,910, filed
June 23rd, 1971, and assigned to the same assignee as the present
application. According to the teachings of this application, at
least one further signal at a frequency lower than the carrier
oscillation of the broadband signal is superimposed on a broadband
signal recorded as a frequency modulated carrier oscillation. The
amplitude of this further signal with respect to that of the higher
frequency broadband signal is selected to be so low that the pickup
edge of the skid-shaped surface of the pickup which is in
engagement with the surface of the record bearing the undulations
when it picks up a number of peaks of the higher frequency
broadband signal which are higher than the average peaks as a
result of a superposition of a lower frequency signal recording,
still contacts the corresponding peaks of the broadband signal
which coincide with a dale in the lower frequency signal recording
and which are consequently lower than the average peaks.
According to this solution of the problem, on which the present
invention is also based, the force with which the pickup surface
presses on the raised portions of the signal recording is
dimensioned or selected so that the highest raised portions on the
surface of the recording are always depressed during playback at
least to the level of the lowest raised portions and the pickup
surface also remains in contact with the individual raised portions
even in the dales of the envelope curve connecting the peaks of the
raised portions. It is clear that in this manner an uninterrupted
scanning of the signal recording is assured but only because the
pressure placed on the pickup surface is selected particularly for
this scanning process. However, limitations result, which in other
respects, according to newer experiences, are undesirable.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to provide an
improved recording carrier which overcomes the above mentioned
problem and, when such a carrier is used for recording and playing
back according to the pressure scanning method, one or a plurality
of additional signal oscillations can be added without there
occurring any unexpected interference during the scanning process
from the different peak levels of the raised portions.
It is a further object of the invention to provide a record carrier
which solves the above problem and which does not result in any
such limitations or restrictions regarding the selection of the
pressure placed on the pickup surface.
The above objects are achieved according to the present invention
in that a recording carrier for storing signals by means of
depressable raised portions in its surface for playback by means of
pressure scanning, which record has a signal recorded thereon which
results in variable heights for the raised portions along the
scanning path according to an envelope function, the distances of
the base planes of the raised portions from a reference plane lying
perpendicular to the extent of the heights of the raised portions
along the pickup scanning path are variable according to one of the
envelope functions of the recorded signal while the peaks of the
raised portions lie substantially in a single peak plane which is
parallel to the above-mentioned reference plane.
In a recording carrier for pressure scanning the raised portions
having different height dimensions form, so-to-speak springs of
different lengths which exert different counterforces on the pickup
surface corresponding to their different lengths, the mutual
compression by the skid-shaped surface of the pickup being
identical. According to the above-mentioned earlier proposals, the
peaks of the raised portions lie on different levels and the
above-mentioned difficulties arise with regard to the maintenance
of a perfect contact by the pickup with those raised portions which
lie in a dale of the envelope curve. In the recording carrier of
the present invention, however, all of the peaks of the raised
portions are substantially at the same level but their base
surfaces lie on the envelope curve which represents the additional
amplitude modulation or which has arisen from the superposition of
the signals. Thus the difficulties regarding safe contact with all
peaks on the part of the pickup are eliminated and the additional
signal is determined by the different height levels of the base
surfaces and thus different spring lengths of the individual raised
portions.
The present invention also relates to the method for recording a
signal on a recording carrier according to the present invention.
According to one embodiment of the method of the invention wherein
the signal to be recorded is a modulated carrier signal whose
positive and negative maximum elongations or amplitudes along the
time axis or base line are variable in size according to
approximately parallel envelope functions, the modulated carrier
signal is amplitude modulated in a special manner with a signal
which is a substantially in-phase or an opposite phase signal
corresponding to one of the envelope functions so that all maximum
elongations or amplitudes in one direction or polarity (positive or
negative) become at least approximately equal with respect to one
another, and the resulting signal is recorded on the carrier as the
signal value in such a direction that the maximum elongations or
amplitudes of identical height result in the peaks of the raised
portions of the record containing the signal recording.
According to a further embodiment of the method of the present
invention for recording a signal on a recording carrier as defined
in the present invention wherein the signal to be recorded is a
modulated carrier signal whose positive and negative maximum
elongations or amplitudes along the time axis or base line are
variable in size according to envelope functions which are
approximate mirror images with respect to the time base line, a
signal which is in-phase or of opposite phase and has substantially
the same amplitude and follows one of the envelope functions of the
modulated carrier signal is superimposed or mixed with the
modulated carrier signal so that all maximum elongations or
amplitudes of the modulated carrier signal in one direction
(positive or negative) become at least approximately equal, and the
resulting signal is then recorded on the carrier as the signal
value in such a direction that the maximum elongations of identical
value result in the peaks of the raised portions of the carrier
containing the signal recording.
According to still a further embodiment of the method of the
present invention for recording a signal on a recording carrier as
defined in the present invention wherein the signal to be recorded
is a modulated carrier signal whose positive and negative maximum
elongations or amplitudes along the time axis or base line are
variable in size according to envelope functions which are
approximate mirror images with respect to the time base line, the
modulated carrier signal is either rectified or the peaks of one
polarity clamped so that all maximum elongations or amplitudes of
the modulated carrier signal in one direction (positive or
negative) become at least approximately equal, and the resulting
signal is then recorded on the carrier as the signal value in such
a direction that the maximum elongations of identical value result
in the peaks of the raised portions of the carrier containing the
signal recording.
The present invention can be used with particular advantage for
recording a resulting oscillation which contains a carrier
oscillation of a higher frequency which is frequency or phase
modulated with a video luminance signal and a lower frequency
carrier oscillation which contains the associated video chrominance
signal preferably in amplitude modulation. To adapt the present
invention to existing standards in the recording of a video signal,
the chrominance signal may be the standard chrominance subcarrier
signal of the PAL, NTSC or SECAM system with a carrier frequency
which has been reduced by down-mixing to such an extent that it
lies below the frequency sweep range of the frequency modulated
broadband signal. According to experiments, a suitable frequency
for the chrominance subcarrier may lie between 300 and 1,000
kHz.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic illustration of an arrangement for pressure
scanning according to the prior art with which the recording
carrier and the method of the present invention can be used.
FIG. 2 illustrates the oscillation signal resulting from the
superposition of two oscillating signals of greatly differing
frequencies.
FIG. 3 illustrates an amplitude modulated oscillation signal or the
oscillation signal resulting from the superposition of two
oscillating signals whose frequencies differ only slightly from one
another.
FIG. 4 is a partial view of a recording carrier of the type used
for pressure scanning whose raised portions containing the recorded
signal were produced by directly recording the signal of FIG.
2.
FIG. 5 is a partial view of a recording carrier of the type used
for pressure scanning whose raised portions containing the recorded
signal were produced by directly recording the signal of FIG.
3.
FIG. 6 is a block circuit diagram of one arrangement with which the
resulting signal of FIG. 2 can be so modified according to the
invention that maximum elongations of the same size result in the
one deflection direction.
FIG. 7 is a partial block circuit diagram of an arrangement similar
to that of FIG. 6 with which the signal of FIG. 3 can be so
modified according to the invention that maximum elongations of the
same height result in one of the deflection directions.
FIG. 8 is a cross-sectional view of a portion of a recording
carrier according to the present invention which can be made by
using the circuit arrangement according to FIG. 6 or a similar
arrangement and by using the signal in FIG. 2.
FIG. 9 is a cross-sectional view of a portion of a recording
carrier according to the present invention which can be made by
using a circuit arrangement according to FIG. 7 and the signal in
FIG. 3.
FIG. 10 is a block circuit diagram of the special amplitude
modulator shown as a block in FIG. 6.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a portion of a recording carrier 1 of the type used
for playback by pressure scanning in a sectional view. The carrier
1 which has grooves 12 corresponds in its stability or rigidity
characteristics to the requirements of the carrier of the
above-mentioned copending application. That is, the carrier has a
modulus of elasticity which is so selected that the raised portions
of its surface contained in groove 12 which represent the signal
recording, are compressed under the pressure of the pickup skid 3
in the direction of the pressure stress by a large amount than the
pickup skid is deflected thereby in a direction opposite to the
pressure direction. The modulus of elasticity of recording carrier
1, or at least of a layer near the surface bearing the grooves 12,
may vary within wide limits within the range of the raised
portions, for example the modulus of elasticity may lie between
40,000 kp/cm.sup.2 and 10,000 kp/cm.sup.2 or even lower. The
recording carrier 1 may have the shape of a circular disc in the
manner of a conventional phonograph record, or it may be in the
form of a tape or strip. The raised portions containing the signal
are disposed in the groove 12 in the surface of the recording
carrier 1. These raised portions may have been produced in the same
manner as a phonograph hill-and-dale recording for example by a
stamping, injection molding or casting process. During playback,
the illustrated portion of the carrier 1 is moved in the direction
of the arrow to the left thereof relative to the pickup skid 3 of a
pickup which additionally includes a mechanical-electrical
transducer 2, for example, a piezoceramic element, and a clamping
member 5 made of a vibration absorbing material. The output voltage
furnished by the transducer 2 is obtained via leads 11 from the
lateral electrical coatings (not shown) of the transducer 2. The
pickup as a whole is fastened to the flattened end 7 of a guide arm
6 whose other end is fastened by means of an elastic joint 9 to a
carriage (not shown) which, when a circular disc-shaped recording
carrier 1 and a spiral groove 12 are used, is guided to correspond
to the radial advance of the pickup. Advancing the recording
carrier 1 in the direction of the arrow causes undulations on the
left-hand side of the pickup skid 3 to come underneath the skid.
However, due to the gradual pressure increase resulting from the
illustrated shape of skid 3 no pulse-type pressure signal is
produced when the undulations on the record surface are being
depressed. Such a pulse-type signal does result, however, when an
undulation appearing in the form of a raised portion leaves the
contact range of the pickup on the right-hand side of skid 3 which
is provided with a sharp edge.
FIGS. 2 and 3 illustrate wave forms which might result, for
example, from the superposition of carrier signals having different
frequencies. The wave form according to FIG. 3 can also be produced
by amplitude modulation. The time pattern t is plotted on the
abscissa while relative amplitude values are plotted on the
ordinate y.
FIG. 2 illustrates the case where two signals with different
frequencies are superimposed. The higher frequency may be, for
example, the frequency of a carrier signal for the luminance signal
of a video transmission, while the signal at the lower frequency
may serve as the carrier signal for a simultaneous audio broadcast.
The higher carrier frequency can be recognized in the rapid
fluctuations visible in the resulting signal and leading to the
formation of the positive maximum elongations 121. The signal at
the lower frequency can be recognized in the bend of the center
line 34 which follows the course of the oscillations at the lower
frequency. In the resulting signal the maximum elongations of the
two opposite directions now lie no longer on an unchanging level,
but rather they show a course according to envelope functions 30
and 31, which are parallel to the center line 34 of the resulting
signal. The carrier signal at the higher frequency may here be
frequency modulated while the carrier signal at the lower frequency
may either also be frequency modulated or amplitude modulated.
FIG. 3 shows in a corresponding manner the pattern of an amplitude
modulated oscillation or the signal resulting from a superposition
of two carrier signals whose frequencies differ only slightly from
one another. As shown in the figure, in this case of superposition,
there then result the known beats, i.e., periodic increases and
decreases in the elongation of the resulting oscillating signal in
the rhythm of the so-called beat frequency. It can be seen that the
maximum elongations or amplitude 13 in the y direction and the
oppositely directed maximum elongations or amplitude 13' have a
time pattern which is illustrated by the envelope functions 32 and
33 and which lie approximately as a mirror image to the center
line, i.e., the time axis, of the resulting signal. This is the
significant difference compared to the envelope curves shown in
FIG. 2 which are parallel to the center line 34.
FIG. 4 is a cross-sectional view through a piece of the recording
carrier 1 whose signal recording was produced in a known manner by
direct conversion of the resulting signal according to FIG. 2 into
a hill-and-dale recording with the aid of an electromechanical
transducer. The spatial recording with the peaks 14 of the
individual depressable raised portions has a cross-sectional shape
which is geometrically similar to the shape of the resulting signal
in FIG. 2, i.e., the peaks 14 and the base areas 14' of the
individual raised portions along time base line t follow the course
of the envelope functions 30 and 31 respectively.
In a corresponding illustration FIG. 5 shows a portion of a
recording carrier 1 in cross section, the recording carrier having
been produced by direct conversion of the resulting signal of FIG.
3 with the aid of an electromechanical transducer. The peaks 15 and
the base areas 15' of the individual raised portions follow, as in
FIG. 3, the envelope functions 32 and 33 respectively.
It can be seen that for a recording carrier according to FIG. 4 as
well as for a recording carrier according to FIG. 5 where the peaks
14 or 15, respectively, of the individual raised portions, do not
lie at constant level or height, the pickup skid 3 of FIG. 1 would
have to be so strongly prestressed that the peaks 14 or 15
respectively would depress the raised portions, even at the points
of the maximum height of the peaks, to such an extent that the
scanning edge of skid 3 would also remain in contact with the lower
peaks of the raised portions lying in the dales of the envelope
curves 30 or 32, respectively. The requirement for such a
presetting of the pickup arrangement substantially narrows the
useful range of the device and is thus undesirable.
FIGS. 6 and 7 show circuit arrangements for producing, with the use
of the present invention, wave forms from the resulting oscillating
signals of FIGS. 2 and 3 in which the maximum elongations in one of
the oscillation directions are all of the same size. If the thus
modified resulting oscillation is then used for recording or
producing the matrix for a recording carrier and the polarity of
the resulting oscillations fed to the electromechanical transducer
is so selected that the peaks of the raised portions correspond to
the maximum elongations of uniform size, there result the spatial
signal recordings as shown in FIGS. 8 and 9 in which the peaks 14
or 15, respectively, lie at the same height and only the base areas
14' and 15' follow an envelope function having a correspondingly
modified shape.
In FIG. 6, the block 16 represents a signal source for a luminance
signal of a video transmission, while block 17 indicates a signal
source for the associated chrominance signal. The output signal of
signal source 16 is fed to modulator 18 wherein it modulates the
high frequency carrier signal produced by carrier signal generator
20 while the output signal of signal source 17 is fed to a
modulator 19 wherein it modulates the lower frequency carrier
signal produced by the carrier signal generator 21. In the
illustrated case the modulator 18 may, for example, be a frequency
or a phase modulator while modulator 19 may, for example, be an
amplitude modulator. Both modulated carrier signals obtained in
this manner are then mixed or superimposed on one another in the
superposition or mixer stage 22 so that the resulting signal
appears as shown in FIG. 2 and as also indicated above the
connection line between stages 22 and 23 in FIG. 6.
The output signal according to FIG. 2 of the superposition stage 22
is fed to the input of the special amplitude modulation stage 23 to
whose other input is fed the output signal of modulator 19, i.e.,
the low frequency carrier signal from source 21 modulated with the
chrominance signal from source 17, so that it is either in phase or
of the opposite phase, i.e., 180.degree. out of phase, with the
envelope function 30 or 31. In the special amplitude modulation
stage 23 the output signal from stage 22 is modulated with the
signal of the lower frequency carrier signal, i.e., the signal from
modulator 19, so that the fluctuations in the height of the peaks
of the signal coming from superposition stage 22 will be
compensated. For this purpose the special modulator shown in FIG.
10 is suitable. There then results an output signal in the form, as
indicated above the output line of special modulator stage 23,
where the maximum elongations of the higher frequency oscillations
in one direction now all lie at the same height, as desired. This
effect is obtained by the special structure of the stage 23 which
is shown in FIG. 10 and which will be described later.
The output modulation signal of stage 23 is then fed to a
conventional electromechanical transducer 25 for producing records
with such a polarity that, when the recording carrier 1' is moved
in the direction of the arrow, uniform peak heights are produced
with base areas which vary in their height in the rhythm of the
modulation. The result is then a matrix or a recording carrier 1 as
shown in FIG. 8 in which the peaks 14 of the raised portions lie in
the same plane 28, which is disposed parallel to a reference plane
29 disposed perpendicular to the extent of the heights of the
raised portions along the scanning path, while the planes of the
base areas 14' are variable in height according to the envelope
curve 30'. The envelope function 30' is here geometrically similar
to the curve of the envelope function 30 or 31, respectively, of
FIG. 2. However, it may also be varied in scale in the direction of
the y axis of FIG. 2.
The special amplitude modulator 23 shown in FIG. 10 consists of a
highpass-lowpass-separating filter 35/36, a usual amplitude
modulator 37 and an addition or superposition stage 38. In this
last stage 38 the low frequency signal of the form of the envelopes
30, 31 is added to the signal of FIG. 3 which is produced by the
usual amplitude modulator 37. The ratio of the amplitude of both
added signals will be such that the resulting oscillation will be
of the form of FIG. 8.
FIG. 7 shows a modification of the arrangement of FIG. 6 which is
particularly suited for the conversion of the curve pattern
according to FIG. 3 into a shape suitable for a recording according
to the present invention. Up to (but excluding) stage 22, the
arrangement according to FIG. 7 is assumed to completely correspond
to that of FIG. 6 so that the parts which are disposed on the left
of stage 22' are not shown again in FIG. 7. It is assumed that the
resulting signal at the output of stage 22' is present in the form
shown in FIG. 3. This signal may be produced by amplitude
modulation of the oscillation coming from modulator 18 with the
oscillation coming from modulator 19. In this case the stage 22' is
a usual amplitude modulator, producing an oscillation which is
symbolically indicated above the connecting line between stages 22'
and 26 of FIG. 7. Provided the case, that the resulting signal
oscillation at the output of stage 22' is a beat signal, this stage
will be a superposition stage. The form of oscillation of FIG. 3
with maximum elongations according to envelope curves which are
substantial mirror images of each other can be converted according
to the invention into the signal indicated at the output of a peak
leveling stage 26 which may, for example, provide a simple
rectification so that the maximum elongations of the high frequency
signal in one of the oscillation directions toward the zero line
now practically lie at an unchanging level. Alternatively, stage 26
could also be constructed in a known manner so that, it provides a
peak rectification of the peaks of one polarity, so that the
maximum elongations in one reference direction (positive or
negative) are brought substantially to a common level. Such a
circuit is often called a clamping or clipping circuit. In the
output line between stage 26 and transducer 25 there again results
an output signal of the pattern indicated by the symbol, but with
double the amplitude compared to the above-described simple
rectification of the signal in stage 26. The output signal of stage
26 is fed, as already described in connection with FIG. 6, to the
electro-mechanical transducer 25 with such a polarity that the
maximum elongations at the same height correspond to the peaks 15
of the raised portions in FIG. 9. These peaks lie, as in FIG. 8, on
the level of the peak plane 28 while the base areas now follow in
their height the envelope function 32' whose course corresponds to
the envelope curve 32 of FIG. 3.
Instead of providing the simple rectification or clamping function
described above, the stage 26 of FIG. 7 may also be replaced by a
stage 26' which linearly superposes two signals. The modulated
carrier signal from the amplitude modulator 22', which is
symbolically indicated above the connecting line between stages 22'
and 26 and whose positive and negative maximum elongations are
variable in size along the time base line according to envelope
functions 32 and 33 which are approximate mirror images with
respect to the time base line, is superimposed in stage 26' with a
signal corresponding to one of these envelope functions and is of
the same or opposite phase and has the same amplitude as the
envelope function. Thus, all maximum elongations in one direction
(positive or negative) become at least approximately equal to one
another so that the wave form which is indicated above the
connection line between stages 26' and 25 is produced which can
then be used in the manner described above to produce a recording
carrier 1 as shown in FIG. 9. In this case the stage 26 may, for
example, include an envelope detecting circuit which detects the
envelope of the input signal to stage 26 and whose output is then
added to the input signal to stage 26 to form the output signal to
be recorded.
FIGS. 8 and 9 thus show cross sections of embodiments of recroding
carriers according to the present invention which can be scanned
according to the pressure scanning method without there being a
need for meeting the undesirable restricting requirements regarding
the contact pressure of the pickup skid 3.
It will be understood that the above description of the present
invention is susceptible to various modifications, changes and
adaptions, and the same are intended to be comprehended within the
meaning and range of equivalents of the appended claims.
* * * * *