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Патент USA US2131293

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Sept. 27, 1938.
'
2,131,293
B. F. MltLER
SOUND RECORDING
2 Sheets-Sheet l
Filed July 5, 1935
3g
57
FIE_2_
Fumnw
4/4
INVENTOR
BUQTON F M11. LEI?
BY
PEA
~
m1»?
ATTORNEY
Sept. 27, 1938.
2,131,293
B‘. F. MILLER
SOUND RECORDING
2 Sheets-Sheet ‘2
Filed July 5, 1955
PIE. 5.
“spar
FB a
INVENTOR. '
Bum-0N F M/LLEP
BY
A TTORN
Patented Sept. 27, 1938
UNITED STATES PATENT OFFICE
2,131,293
SOUND‘ RECORDING
Burton F. Miller, Hollywood, Calif., assignor to
United Research Corporation, Long Island
City, N. Y., a corporation of Delaware
Application July 5, 1935, Serial No. 29,931
2 Claims. (01. 179-1003)
This invention relates to sound translating de- taken along the line I—I of Fig. 2 and diagram
vices and particularly to improvements in light matically showing the arrangement of an optical
valves for use in recording sound by the varia- system associated therewith.
ble area method upon a photographic medium.
Fig. 2 is a sectional view taken along the line
The invention is particularly adapted to be
used in recording sounds to be later reproduced
in synchronism with motion pictures.
In this type of light valve a narrow slit having
a width in the order of about one-half mil is
10 provided through which a beam of light is projected onto the sensitized surface of a uniformly moving ?lm. A vibratory current carrying conductor is placed in an angular position
2——2 of Fig. 1.
5
Fig. 3 is a longitudinal section taken along the
line 3-3 of Fig. 2.
Fig. 4 is an enlarged fragmentary view of the
light slit and its associated vibrating conductor.
Fig. 5 shows the length of ?lm having a varia- 10
ble area sound track thereon, as produced by
the light valve.
Fig. 6 is a schematic view showing the applica
5
over the slit so as to allow about one-half of the
15 length of the slit to be exposed to the beam of
light when no current is ?owing through the
conductor. A strong magnetic ?eld having its
?ux at right angles to the plane of the conductor
is provided by a magnetic frame having its poles
20 placed closely adjacent the slit and conductor.
When an alternating speech current is passed
through the conductor the interaction between
the magnetic ?eld and the magnetic force produced by the current ?owing through the con25 ductor causes the conductor to vibrate back and
forth in accordance with the amplitude and frequency of the current thus changing the length of
the exposed portion of the slit to the beam of
light.
30
In my ore-pending application Serial No.
28,109, ?led June 24, 1935, for Sound recording, I have disclosed and claimed a light valve
having a single electrical conductor vibratile at
the frequencies to be recorded which is placed
35 across an aperture for producing a noiseless
sound track of the double hump type. While it
contains claims generic to the arrangement disclosed in detail here, that case speci?cally dis~
closes the use of a triangular aperture in the
40 path of the recording light beam, the single conductor moving parallel to the base of the tri-
angular aperture.
An object of the present invention is to adapt
the apparatus of my co-pending application rei.» ferred to above to the recording of a noiseless
sound track of the single hump type.
This is accomplished by modulating the recording light beam by means of a single conductor
moving angularly with respect to a rectangular
50 slit,
The invention further relates to improvements
in the mounting for the single string conductor.
This invention is illustrated in the accompanying drawings in which:
55
Fig. 1 is a transverse section of a light valve
tion of a noise reduction circuit.
Figs. 7 and 8 are diagrammatic views showing
the method of adjusting the biasing of the
vibratile conductor.
Fig. 9 is an enlarged fragmentary view of a
positive ?lm having a variable area sound track
resulting from the use of the noise reduction circuit shown in Fig. 6.
Fig. l0 is an enlarged fragmentary view Show
ing a sound track produced by the noise reduc~
tion circuit in Fig. 6.
Referring now to Fig. 1, an exciter lamp I of
constant intensity projects a beam of light 2
through a pair of condenser lenses 3. from
whence it is focused to a point F within the light
valve generally indicated at 4. Here the beam of
light 2 is changed into a narrow slit of light
of varying length. An objective lens 5 focuses
the slit of light upon the sensitized surface of
a continuously moving ?lm 6.
Referring now to Figs. 1, 2, and 3, the light
15
20
25
30
valve 4 comprises a magnetic frame made up of 35
a base plate ‘I of magnetic material, which is se~
cured at its outer ends to the depending legs 3
and 9 of an upper magnetic frame Ill by means
of screws II. The upper frame I 0 has a hollow
core I2 provided thereon, which acts as one pole 40
of the magnet. A magnetic coil l3 receives a
substantially constant direct current to produce
a magnetic ?ux between the core l2 and a pole
piece !4, which is secured to the lower base plate
‘l in alignment with the core l2, as shown in Fig. 45
1. The pole piece i6 is provided with an a er~
ture l5 to allow the beam of light to be pro
jected therethro-ugh. The ends of the core If!
and the pole piece M are placed closely adjacent
each other so as to produce as strong a magnetic 50
flux as P08811318
Mounted on the base plate 1 adjacent the pole
piece M are a pair of bridges I6 and H, having
raised portions 18 and I9, upon which a vibrating
conductor 20 rests. The bridges l6 and I‘! are 55
2
2,131,293
formed of insulating material such as Bakelite or
hard rubber. The conductor 20 is secured. at one
end to a Windlass 2|, for the purpose of adjusting
the tension of the conductor 20. The other end
of conductor 20 is passed around a spring pressed
arm 23 and is secured to a Windlass 25 similar to
that of 2!. The arm 23 is pivotable about a stud
24 and is urged outwardly toward the leg 8 by
a torsion spring ti thus serving to prevent undue
10 tension from being placed upon the conductor 20.
The windlasses 2i and 25 are electrically con
nected by means of conductors 46 and 41 to ter
minals 22 and 35 which, in turn, are connected
through wires 56 and 5'! to suitable sound record
15 ing ampli?ers not shown. When a current is
passed through the coductor 20, the interaction
between the magnetic ?eld set up by the con
ductor 2i] and the magnetic ?eld between the
hollow core l2 and the pole pieces l4 and I5 will
20 cause a movement of the conductor 20 to one
side or the other depending on the direction of
the current.
Referring now to Fig. 1, the beam of light 2
is focused upon a slit 34 de?ned by a pair of
25 slit forming members 26 and 2'! which are se
cured upon supporting members 28 and 29 by
means of clamping plates 39 and 3!. The sides
of the members
and 2'! are engaged by a pair
of transversely extending plates (l8 and 49, also
30 secured by means of the clamping plates 3% and
Si to de?ne the ends of the slit 3G. Of course,
it should be understood that the slit 34 may
and the slit 34 and also the initial position of the
conductor 20 at no modulation may be varied.
At Fig. 5 is shown a section of a positive print
of a moving picture ?lm 44, having a variable
area sound track portion 45 at one edge thereof
formed by the passage of the ?lm before the light
valve 4,
Referring to Figs. 6, 7, and 8, I will now de
scribe the application of noise reduction to the
recording of sound by my improved light valve. 10
The recording circuit (Fig. 6) comprises a micro
phone EG wherein sound waves are received and
are translated into electrical currents of equiva
lent wave form and proportionate amplitude. In
circuit with the microphone 5B is an ampli?er 5|
and a transformer 52 which supplies an ampli
?ed audio frequency current to the vibrating
conductor 26 of the light valve 4. A noise re
duction ampli?er 53 and recti?er 54 are shunted
across the light valve circuit to provide a bias 20
neutralizing current through the conductor 20.
Biasing current is provided by a battery 6i so as
to hold the conductor 29 in the position shown
by the dot and dash lines 29 of Fig. 4 when. no
or little sound is being recorded. Thus the center
of modulation as represented by the line 58 (Fig.
9) is held to the left of the center of the sound
track 59 when recording low level sounds as at
point L. When high level sounds are recorded,
a current which increases in proportion to the 30
increase in level of the sound is impressed upon
the ampli?er 53 and recti?er 54. The recti?ed
also de?ned by the edges of the pole piece 14.
current is fed to the conductor iii in a direction
The members 22 and 29 are secured to the base
35 plate I by means of screws such as 32 and 33.
Referring now to Fig. 4, the vibrating con
opposite to that fed by the battery iii to thus
neutralize the biasing current produced by the
battery 6i. This neutralizing of the biasing cur
ductor 29 is so adjusted with respect to the slit
34 formed by the members 26 and 2'! that it
crosses it at a slight angle, which in the present
40 instance is slightly over one degree.
Due to the
fact that the natural period of vibration should
preferably be above the range of audibility, it
is necessary to keep the mass of the conductor 20
as small as possible. In this instance the con
ductor 263 is in the form of a ?at ribbon about
.0005" thick and about .006" wide and is con
structed of Duralumin or other light material.
These dimensions of course may be varied in
accordance with different conditions and re
quirements. When no current is ?owing, the
conductor 29 covers approximately one—half of
the area of the slit 34. When an alternating cur
rent causes the center of modulation of the con
ductor 2E1 to take a position shown by the full
lines of Fig. 4. Thus the center of modulations
for high level sounds as shown at point H (Fig.
9) is shifted toward the center of the sound
track 59.
The amount of biasing of the conductor is gen
erally dependent upon the kind of sound being
recorded.
When recording dialogue or music in .
which the volume is low, or where the change in
volume is gradual, the main biasing position of
the conductor may be brought nearer to its clos
ing position than in the case of recording stac
cato sounds such as are produced by a piano or
harp.
In recording the latter type of sound,
rent is passed through the terminals 22 and 35,
more leeway has to be given to the conductor to
prevent the high level wave forms from being
the conductor 26 is caused to move in a direction
clipped.
55 perpendicular to the magnetic flux between the
hollow core l2 and the pole piece M so as to
change the length of the exposed portion of the
slit M. The tension and angle of the conductor
2E5 is so adjusted that at full modulation the
60 entire slit 34 is covered at one instant while at
another instant the whole area of the slit is ex
posed. This exposure of the slit 34 is, of course,
directly proportional to the amplitude of the
current passing through the conductor.
In order to provide adjustment of the conductor
(i5
This change in biasing position of the
conductor is accomplished by means of variable
resistance 63 (Fig. 6) and may be effected during
recording whenever the tempo of the sound is
changed. The change may be made between dif
ferent types of recordings when the recorder is
stopped or during operation of the recorder when 60
the operator is aware of the nature of the sound to
be recorded before impression thereof.
The amount of biasing is generally determined
by the amount of margin betwen a depression of
a wave form and the edge of the sound track as
justably secured to the bridges l6 and I‘! by
indicated at M (Fig. 8). Referring to Figs. 7 and
8, the margin may also be determined by the dis—
tance from the left hand edge 65 of the light slit
34 to the position of the conductor 20 at the
upper limit of its excursions as indicated by the 70
dotted line 55. In setting the biasing position of
the conductor 2%, the variable resistance 63 is
manipulated until the distance X, representing
means of adjusting screws 42 and 43.
one-half of the amplitude of the conductor excur
26 in relation to the slit 3d, the bridges l5 and
l? have adjusting jaws 36, 37, 3S and 39 thereon.
These jaws are preferably formed of a spring ma
terial and are secured at their rear ends to the
70 bridges l6 and I’! by screws 40 and M.
The
forward ends of the jaws are bent inward to en
gage the sides of the conductor 20 and are ad
Thus,
75 both the angle made between the conductor 20
sions at an arbitrary low level single frequency 75
2,131,293
sound, is allowed to reach a certain percentage
.of the distance D (between the zero line of modu~
lation in the biasing position and the edge of the
sound track) ; this percentage, of course, depend
ing on the type of sound being recorded. In
recording soft sounds, the distance X may be
allowed to cover as much as 85% of the distance
D.
In the example shown in Fig. 8, the variable
10 resistance 63 is set so that X will equal one-half
D when the conductor is in its biased position.
Thus, the margin for low level sounds is indicated
by the dimension M. When the amplitude of the
sounds is increased to a point at which X exceeds
one-half D the change in biasing current causes
the mean position of the conductor 20 to be moved
downward so as to maintain approximately the
same average ratio of X to D. This ratio will re
main approximately constant until the conductor
20 20 reaches its unbiased position as shown by the
dotted lines 20'. In this position the ratio of M1
to D1 is still approximately equal to the ratio
of M to D. As higher amplitudes are recorded,
the zero line of modulation remains at C, provi
25 sion being made in the recti?er R to prevent a
shift of the zero line to the right of C, while the
margin again becomes smaller as at Mh to ac
commodate the higher amplitudes.
Referring to Fig. 9, the zero line of modula
30 tion is indicated by the center line 58. Where no
sound is recorded on the ?lm only a narrow path
of transparency 61 traverses the sound track. As
modulations are recorded and increased, the zero
line of modulation is moved outwardly toward
35 the center of the sound track until the conductor
reaches its unbiased position as indicated by the
point H.
40
45
50
55
Due to the fact that the edges of the sound
track are formed by the acute angle between the
conductor 20 and the light slit 34, these edges
will not form sharp lines but will gradually pass
from clear transparency to opacity as shown in
Fig. 10. The amount of distortion, however, pro
duced by this shaded zone 68 is negligible due to
the fact that its dimension as measured trans
versely of the direction of the ?lm travel remains
constant and thus it is unable in itself to mate
rially effect a varying change of light passing
therethrough; it being understood, of course, that
the reproduction of sound is dependent upon a
change in the amount of light passing through the
slit above the lowest audible frequency. The
only possible effect of the shaded zone caused by
frequency variations in the sound being recorded
is to vary the direct current component, which
does not change the frequencies making up the
sound wave.
3
The biasing of the conductor 20 may also be ac
complished by applying the recti?ed current from
the recti?er 54, which varies in accordance with
the amplitude of the sounds being recorded, in a
positive sense to the conductor 20. In this case,
the normal position of the conductor 20 would be
mechanically adjusted so that at low level modu
lation it would be to the left of the center of the
sound track or in a position shown by the full
lines 20 of the conductor Fig. 7. With the in 10
crease in amplitude of the sound being recorded,
the corresponding increase in recti?ed current
from the recti?er 54 would shift the center of
modulation of the conductor 20 to the position
shown by the dotted lines 20'. That is, instead of 15
variably neutralizing a ?xed electrical bias, the
?xed electrical bias is eliminated and the recti?ed
current variably biases the conductor in accord
ance with the average amplitude of the sound
waves being recorded.
20
Having thus described the invention what is
claimed as new and desired to secure by Letters
Patent is:
1. A device for recording sound waves which
comprises a system for transmitting light from a
source to a photographic ?lm, means for varying
the amount of transmitted light comprising a
member arranged in a magnetic ?eld and having
an elongated slit therein, a single electrical con
ductor arranged in the same magnetic ?eld as 30
said member and adjacent the slit in said member
to de?ne a light transmitting slot, means for sup
plying electrical current to said conductor to
e?’ect variation in the space relation between said
conductor and said slit in accordance with the in 85
stantaneous values of said currents, and means
for supplying a current to said conductor to
effect a variation in the spaced relation of said
conductor with respect to said slit in accordance
with the envelope of said electrical currents, said
conductor and said slit being disposed in oblique
relation to each other.
2. In combination, a member located in a mag
netic ?eld and having a ?xed elongated aperture
therein, the same movable element suspended in 45
a magnetic ?eld and disposed in oblique relation
to the aperture in said member, means to supply
modulated electrical currents to said movable ele
ment to effect movement thereof in front of said
aperture in said member in accordance with the
50
instantaneous values of said currents, and means
to supply current to said movable element to
effect movement thereof in front of said aperture
in said member in accordance with the envelope
of said electrical currents.
55
BURTON F. MILLER.
CERTIFICATE OF CORRECTION.
Patent No. 2,151,295.
September 27, 1958.
BURTON F. MILLER.
It is hereby certified that error appears in the printed specification
of the above numbered patent requiring correction as follows: Page 5, second
column, line k5, claim 2, for the words "the same" read a; line k6, same
claim, for "a" read the same; and that the said Letters Patent should be
read with this correction therein that the same may conform to the record
of the case in the Patent Office.
Signed and sealed this 21st day of March, ‘A. D. 1959.
Henry Van Arsdale.
(Seal)
Acting Commissioner of Patents.
CERTIFICATE OF CORRECTION.
Patent No. 2,151,295.‘
'
-
-
September 27.1958.
BURTON F. MILLER.
It is hereby certified that error appears in the printed specification '
of the above numbered patent requiring correction as follows: Page 5 , second
column, line 1L5, claim 2, for the words "the same" road a; line liéysame
claim, for "a" read the same; and that the said Letters Patent should be
read with this correction therein that the same may conform to the record
of the case in the Patent Office.
Signed and sealed this 21st day of March, ‘A. D. 1939.
Henry Van Arsdale.
(Seal)
Acting Comissioner of Patents.
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