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Патент USA US2109452

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March 1, 1938.
‘G. L. D‘IMMICK
‘
2,109,452
RECORDING OF SOUND
Filed Nqv. 2, 1935
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INVENTOR
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BY'
ATTORNEY
Patented Mar. 1, 1938
2,109,452“
UNITED STATES
PATENT OFFICE
2,109,452
RECORDING OF SOUND‘v
Glenn L. Dimmick, Audubon, N. J., assignor
to 1
Radio Corporation of America, a corporation.
of Delaware
, Application November ‘2, 1935', Serial No. 47,968
9 Claims.
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(01. 179¢+100.3)
“ This invention relates to the recording of sound
ture l2 of a mask l3 and a lens M to the galvanom- eter recorder mirror l5 which ‘is vibrated i111 ac~
cordance with the signals to be recorded. Light
or the like, and has for its principal object the
provision of an improved apparatus and method
of operation for obviating certain kinds of distor
tion which tend to occur in the reproduction of
sound from a multiple track or push-pull record
such as that disclosed by my copending applica
tion Serial No. 674,805, ?led June 8, 1933 and as
signed to the same assignee as the present ap
plication.
As pointed out in the aforesaid copending ap
plication, the distortion caused by fogging of the
record valleys and under-exposure of the record
peaks is avoided by the provision of two similar
sound tracks displaced in phase by 189 degrees and
is re?ected from the mirror [5 through a lens Hi,
the light slit I‘! of a screen [8 and lenses l9 and
29 to the light sensitive surface of a record strip
25 which is supported upon and moved over the
surface of a roller 22.
The image of the aperture l2 re?ected by the
mirror i 5 onthe member I 8 is indicated at 23.
As will be readily understood, this image is‘ in the 10
form of a parallelogram offset at its opposite ends,
is vibrated transversely of the slit and produces
two sound tracks 24 and 25 (Fig. 3) which are dis
arranged to be simultaneously reproduced and
combined for operating a loudspeaker or the like.
While the types of recorder disclosed by the afore
said application obviate the distortion mentioned
above, their operation sometimes involves the
di?iculty that the separate sound tracks tend to
overlap at high modulation and are not readily
reproduced without distortion when such over
lapping occurs. In accordance with the present
IO Ll invention, such distortion of the reproduced sound 1
is minimized or avoided by the provision of means
for producing a light beam of such con?gura
tion that the two sound tracks are maintained in
spaced relationship with one another irrespec
tive of the extent to which they are modulated.
As hereinafter indicated, one suitable means of
determining the contour or shape of the light
beam is a mask having an aperture provided with
a central portion having its edges sloped with re
spect to a cooperatively associated light slit and
with end portions having their opposed or inner
‘edges perpendicular to the light slit and spaced
apart to maintain a predetermined spacing be
tween the two record tracks. For convenience of
This form of aperture has the
advantage that overshooting of the light beam due
to excessive modulation can not cause one ‘of the,
modulation is avoided.
I claim:
,_
1. A signal recorder including means de?ning
a light slit, means for producing a light beam
having the form of a parallelogram offset to
space its ends from one another along the length
‘
'
slit,
and signal responsive
means operable to vibrate said beam across said
slit transversely to said dimension.
35
expression, this aperture is sometimes hereinafter
designated as having the form of a parallelogram
oil‘set at its opposite ends.
The invention will be better understood from
the following description when considered in con
nection with the accompanying drawing, and its
scope will be pointed out in the appended claims.
Referring to the drawing,
record, and means for moving said record trans
versely of the light transmitted through said slit.
3. A sound recorder of the galvanometer type
including means de?ning a light slit, means for
producing a light beam provided with a central 45
Fig. l is a diagrammatic showing of a recorder '
constructed in accordance with the invention,
Fig. 2 illustrates the form of the light beam and
its relation to the light slit, and
Fig. 3 illustrates the type of record produced by
the recorder.
across said slit.
-
4. In an apparatus for producing sound tracks 50
displaced in phase
The recorder includes a light source I 0 from
which light passes through a lens II, the aper
55
2,109,452
2
portion, means de?ning a light slit, and signal
responsive means operable to vibrate said beam
across said slit.
5. In an apparatus for producing'sound tracks
180 degrees out of phase with one another, the
combination of means de?ning a light slit, means
for producing a, light beam having its end por
10
tions spaced apart longitudinally of said slit and
angularly disposed with respect to its central
portion, and signal responsive means operable to
vibrate said beam across said slit in a direction
parallel to the side edges of said end portions.
6. In a signal recorder including means de?n
ing a light slit and signal responsive means oper
able to vibrate a light beam transversely across
15
said slit, means for producing a light beam
having the form of a parallelogram offset to space
its ends from one another along the length di
mension of said slit.
'7. In a signal recorder including means de?n
20 ing a light slit, signal responsive means operable
to vibrate a beam of. light transversely across
said slit, a light sensitive record, and means for
moving said record transversely of the light
transmitted through said slit, means for direct-'
ing a beam of light having the form of a paral
lelogram o?set to space its ends from one another
along the length dimension of said slit to said
signal responsive means.
8. In a sound recorder of the galvanometer
type including means de?ning a light slit and
means for vibrating a beam of light across said
slit, means for producing a light beam provided 10
with a central portion angularly disposed with
respect to said slit and with end portions per
pendicular to and spaced apart along said slit.
9. In an apparatus for producing sound tracks
displaced in phase with respect to one another 15
and including means de?ning a light slit and
signal responsive means operable to vibrate a
beam of light across said slit, means for pro
ducing a light beam having its end portions
spaced apart and angularly disposed with respect 20
to its central portion.
GLENN L. DIMMICK.
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