US2184548A - Recording of electrical impulses - Google Patents

Description

G. L. DIMMICK RECORDING 0F`ELECTRICAL IMPULSES Dec. 26, 1939.

2 Sheets-Sheet l Filed June 25, 1938 Gtfotneg Dec. 26, 1939. G. l.. DIMMlcK 2,184,548

RECORDING 0F ELECTRICAL IMPULSES Filed June 25, 1938 2 Sheets-Sheet 2 ig F595 %f47 y Ig/1%' ,60

/l=,j=r/` v 4 l 4a F595 F592- @f0- Suventor Patented Dec. 26, 1939 RECDRDING OF ELECTRICAL R'IPULSES Glenn L. DimmickyHaddoneld, N. J., assigner to Radio Corporation of America, a corporation of Delaware Application June 25, 1938, Serial No. 215,910

1.0 Claims.

This invention relates to the recoiding of electrical impulses such as those of audio frequency, and has for its principal object the provision of an improved recording apparatus and method of operation whereby overshooting of adjacent records one onto the path of the other is avoided'and the operation of such apparatus is simplified and improved. This application is in part a continuation of my application Serial No. 181,593, iiled December 24, 1937.

The invention is Amore particularly adapted to the recording of plural track records such as those of the double-hump type, the push-pull type and the like. OneN of its distinguishing characteristics is the utilization of a pair of differently polarized light beams which are enlarged as the signal modulation increases. These beams are separated by an opaque area which is decreased in size as the signal modulation increases and which altogether disappears at extremely high signal modulation or overshooting. Although the use of polarized light is preferred, I may accomplish substantially the same result by using an appropriately complementary color screen.

In a preferred form of the invention, the dilTerently polarized light beams are moved outwardly from the center of the record track in response to increase in the signal modulation and Vice versa. Since the opaque area intermediate the adjacent records forms the inner edge of the adjacent record tracks and this opaque area is obliterated at overshooting or extremely high modulation, interference of one track with the other is altogether avoided.

of each beam to a separate area of the light slit` and preventing interference of the adjacent record track areas.

The polarizing material utilized to produce these various effects may be of any suitable form such, for example, as the commercial product commonly known as polaroid.

The invention will be better understood from the following description considered in connection with the accompanyingr drawings and its scope is indicated by the accompanying claims.

Referring to the drawings',

Figure 1 illustrates a system including a preferred form of the invention,

Figures 2, 3, 6 and 7 are fragmentary drawings illustrating the essential features of modified forms of the invention,

Figures l and 5 are explanatory diagrams relating to the distinction of the inventionpver somewhat similar prior art systems,

Figure-8 is al type of class A push-pull recordY produced by the arrangement of Figs. 6 and 7,

Figure 9 is a double hump reccrd'produced by a recording system of the type illustrated by, Fig.

l, and

Figure l() is a similar type of class A push-pull record produced by the arrangement of Fig. 3.

lThe recording'sys'tem of Figgl includes a pick.- up device or microphone l' from which the impulses to be recorded are supplied through ampliers ll and. l2- to the operating coil I3 of a re. cording galvanometer i4. Light from a source l5 is projected through a lens i6, the triangularly shaped aperture of an aperture plate il', a pair oi diierently polarized movable varies i3 and i9 and lenses 20 and 2i to the `mirror of the galvanometer lll.

The differently polarized kvanes lll and i9v are movable transversely of the aperture of the plate ll and are illustrated as overlapping at their adjacent ends. The extent to which they overlap is determined by their control mechanism which is energized in accordance with the envelope current or volume of the recorded impulses. To this end, a component of the recorded impulses isv supplied through a rectifier and lter network 22 to an operating coil 23 which acts through a lever "24 and a resilient member 25 to move the vane supporting arms 26 and 2l in response toy change in the volume or amplitude of the recorded impulses. It will be observed that the lever 24 is pivoted at 2S and' is biased by means of a spring 2l which opposes the pull of the coil 23 on the lever. Under these conditions the vanes i8 and I9 are moved transversely of the aperture of the plate ll in accordance with the signal level. The light beams have their contour outlined by the noncverlapping areas 23 and 29, which vary in size in accordance with the signallevel. f

The differently polarized beams dened by the areas 28 and'ES 'are applied to the mirror of the galvanometer llt and from this mirror are reflected to the recording surface 3B through the lens 2l, the light slit of a plate 3l and lenses 32 and 33. The images of these dilierently polarized light beamsare indicated at- 365 and 35 on the light slit plate 3l. Since the spacing between these images is determined by the overlapped or opaque area of the vanes i3 and l 9, and this overlapped area is dependent on the level of the re.- corded impulses, it will be apparent `thatovershooting of the beams in a manner to cause in` iii . terference between the adjacent record tracks is avoided. The resulting type of record is shown in Fig. 9 wherein the two component records are indicated at 36 and 3l and the shading produced by the intermediate opaque area is indicated at 38. It will be observed that when the vanes |8 and I9 are moved outwardly to a point where they do not overlap, the intermediate opaque area 38 ceases to exist and the extension of one of the 10,l component records into the track normally oc- 50 accordance with the volume or envelope of the recorded impulses. With this arrangement, the overlapped central area of the light slit is opaque and the width of this area is increased and decreased longitudinally of the slit so as to variably shade the central part of the record in pull record illustrated by Fig. 10.

of the light slit of the plate 3|.

the manner previously explained in connection with Fig. 9.

Fig. 3 illustrates a similar modification of a recorder suitable for producing the class A push- As in the lmodification of Fig. 2, the light beams 4|J and 4| are overlapped at their adjacent ends and are vibrated longitudinally of the light slit in n accordance with the volume of the signal to be recorded. The recording beam itself, however, is in the form of a trapezcid having its ends displaced With respect to one another. The operation of this modication of the invention will be apparent in View of the previous explanation. Thus, at relatively low modulation of the recorded impulses the differently polarized beams 40- and 4| are overlapped to a comparatively great extent and the central opaque portion 42 of the record is comparatively wide. At relal' tively high modulation of the impulses, however,

this central opaque area 44 decreases in width and finally disappears at extremely high modulation which would otherwise produce interference between the adjacent record tracks 45 and 46.

Diierent prior art arrangements for recording a class A push-pull record are illustrated by Figs. 4 and 5. Thus, in Fig. 4, a light beam of the shape indicated at 4'| is vibrated transversely It will be observed that the opposed ends of this beam are offset to prevent interference between the different record tracks. The type of record produced by this arrangement is indicated by the central area 48 of the record of Fig. 8. In the somewhat similar arrangement of Fig. 5, a pair of similarly shaped light beams 49 and 50 are vibrated transversely of the light slit of the plate 3|. This arrangement, of course, results *in a negative sound record which is the reverse of that produced by the arrangement of Fig. 4. In the arrangement of Figs. 6 and '7, a pair of rectangular light beams 50 and 5| are vibrated longitudinally of the light slit of the plate 3| to produce a record such as that shown by Fig. 8. In this modification, the light slit has associated with its opposite halves differently polarized materials as indicated at 42 and 43 of Fig. '7, the light slit part 42, for example,

5 being associated with the similarly polarized beam 50 and the light slit part 43 being associated with the similarly polarized beam 5|. At overshooting the polarized beams pass beyond the center of the slit and, of course, their light is excluded by the diierently polarized light slit section and interference of the records, one with the other, is thereby prevented as indicated in the record of Fig. 8.

In any of the above-described species of the invention, I may substitute a color lter for one of the polarizing screens and a complementary color filter for the other of said screens, the exact relation of the colors chosen depending upon the characteristics of the film which is to be used. For use with panchromatic film, I may use one filter of orange red and the other filter of grennish blue, while, for film sensitivity in the blue and near ultra violet regions only, I may use one lter which is transparent to the near ultra violet and not to the blue, and another filter which is transparent to the blue but opaque to the ultra violet and other combinations of filters that may be chosen according to the particular characteristics of the film. The filter, however, should preferably transmit light having approximately equal actinic effect upon the lm so that the respective film areas will be exposed to the same degree. For instance, with an ortho type of film, if one filter has a high transmission in the blue, the band of transmission of this lter should be relatively narrow or its density should be relatively high, while the complementary filter should transmit as much of the spectrum as possible due to the lower sensitivity of the film to the other regions of the spectrum.

I claim as my invention:

1. An electrical impulse recorder including means for producing a plurality of light beams, means for diierently polarizing said beams, means for modulating said beams in accordance with the impulses to be recorded, and means for varying the areas of said beams in accordance with the level of said impulses.

2. An electrical impulse recorder including means for producing a plurality of light beams, means including a pair of vanes movable in opposite directions for diierently polarizing said beams, means for modulating said beams in accordance with the impulses to be recorded, and means for moving said vanes in accordance with the level of said impulses.

3. The combination of means for dening a light beam, means including a pair of partially overlapped vanes for converting said light beam to a pair of differently polarized light beams, means for modulating said pair of light beams in accordance with the impulses to be recorded, and means for varying the overlapping of said vanes in accordance with the level of said impulses.

4. An electrical impulse recorder including means for producing a plurality of differently polarized light beams, light slit means diierently polarized as at its opposite ends, and means for vibrating said polarized beams transversely of said slit means in accordance with the impulses to be recorded.

5. The electrical impulse recording method which includes producing a plurality of differently polarized light beams, modulating said beams in accordance with the impulses to be recorded, and varying they size of said beams in accordance with said impulses.

6. An electrical impulse recorder including means for producing a plurality of light beams.

means including a pair of vanes movable in opposite directions each transparent to light of a characteristic to which the other is opaque, means for modulating said beams in accordance with the impulses to be recorded, and means for moving said vanes in accordance With the level of said impulses.

'7. The combination of means for defining a light beam, means including a pair of partially overlapped vanes for converting said light beam to a pair of light beams having diierent characteristics, each Vane being opaque to light havingthe characteristics transmitted by the other vane, means for modulating said pair of light beams in accordance with the impulses to be recorded, and means for varying the overlappingA of said varies in accordance with the level of said impulses. y

8. An electrical impulse recorder including means for producing a plurality of light beams having diierent characteristics, light slit means having means at its opposite ends transparent to light of one of said characteristics and opaque to light of the other of said characteristics, and means for Vibrating said beams transversely of said slit means in accordance with the impulses to be recorded.

9. An electrical impulse recorder including means for producing a plurality of light beams, means including a pair of complementary color varies movable in opposite directions for differently coloring said beams, means for modulating said beams in accordance with the impulses to be recorded, and means for moving said vanes in accordance with the level of said impulses'.

10. The combination of means for deiining a light beam, means including a pair of partially overlapped vanes for converting said light beamv Cil

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