US1939726A - Reproduction of sound - Google Patents

Description

Dec. 19, 1933. J. sH W I HEPRQODUCTIONZVOF SOUND Filed July :50, i930 IN V EN TOR. Jbsnw ASH/4W M4, A TTORNEYS.

Patented Dec. 19, 1933 7 1,939,726 REPRODUCTION OF SOUND Joseph Shaw, Hastings-ori-Hudson, N. Y., as-' signor to Paramount Publix Corporation, New

York, N. Y., a corporationof N ew -York Application July 30, 1930. Serial No. 471,642

10 Claims. (01. 179-1003) This invention is directed to sound'reproduction, and specifically to reproduction of sound photographically recorded on a'film.

One of the objects of my invention is the-provision of a method and apparatus whereby superior results are obtained as compared with prior methods and means, my invention providing clearer and better definition and greater intensity with a given power input.

10 A still further object of my invention is the provisionof a method and apparatus for use in been recorded in theform of images of different degrees of densityfas distinguished from images of varying width.

In the reproduction of sound-so recorded it has been the custom to project the rays from a light source of fixed intensity througha condenser lens system, a light slit of fixed dimen sions and an objective lens system upon thesound images on the film, the light rays which pass through the' film falling upon the window of'a photoelectro cell connected in an electric circuit. With such systems it has been found that pencil of light isfo'c'usedupon the film, and better results when a very narrow slit aperture isplaced' between the optical'sy'stem and the lightsource, the focusing of a very narrow pencil jof light upon the film reducing the 'overlapping of the frequency image lines on the film, thereby to' improve reproduction, I

" However, the narrow slit has its disadvantages filament lamp it is difilcult for theaverage projectionistproperly to focus the light on the film,j

much trouble and poor reproduction resulting from the lamp being out of alignment with the central axis of the light slit and from sagging of, the filament to throw the light image: line out of. focus. This latter causes blurred reproduction and loss of high frequencies.

Another objection to the use of the very narrow light slit is the light interference which resultsfromyprojecting light through a narrow slit, a phenomena Well recognizedinphysicsnand 05 which'if great. care is notexercised: in. properly best results are obtained when a very narrowand drawbacks inasmuch as it involves loss of j light, and furthermore when using the narrow slit and a lamp. with a coil filament or a ribbon proportioning the slit also results in distorted reproduction.

I have found by a great number of trials that the drawbacks, some of which have been enumerated above, can. be overcome by using one 03 or more highly restricted circular apertures of" the nature of pinholes in front of the film, i. e., between the film and photoelectric cell. By. my method and apparatus the light source is focused on the-film, the light rays after passing through 65.

the sound film passing through the minute aperture or apertures and from thence to the photoelectric cell.

- I have found in practice that the sharper the photoelectric cell emission, the less amplification required, theemployment'of a highly restricted aperture i. e. a pin hole aperture between the film and cell I am able to obtain a better concentration of the light rays than possible with. the usual elongated aperture with a resultant in- 75. creasein the emission efiiciency. of the cell.

Consequently, comparing the results produced with the usual light slit employed in reproduction with the results produced by meiwhen employing the highly.restrictedfaperture or apertures of this invention, the volume of reproduced sound is relatively increased.

I havediscovered also that the highly restrict-' ed aperture or apertures placed as inventedby me function as a lens'system to focus the sound v images upon the surface of the V photoelectric cell, the smaller the aperture the better theresults obtained, theuseof my invention, therefore, improving the quality of reproduction.

The increased volume obtainedby me, therefore, I attribute to the increased emission pressure upon the surface of the photoelectric cell covered by the concentrated light rays passing through the highly restricted, minute aperture employed by meascompared to the effect of the light rayspassing through a slit as in present practice.

i The better sound definition obtained by the use of my invention I attribute to the use of a minute aperture intermediate the film and cell and so placed with respect to the film that only the light rays passing through a single frequency image at a time are projected uponthe cell, therebyavoiding the frequency overlapping, asmet with in present practice. I

Itwill be appreciated also that inasmuch as the aperture is in front of the film,- i. e., between, the film and, the lightsensitive electric deviceorcell, the, projectionistis not called upon constant- 1y to watch the filament of the light source to see as the light rays under my invention are not focused upon a restricted light slit before striking the film, as under present practice, but are projected directly upon the film, so that even with reasonable sagging of the filament the light rays will still strike the film and cover the minute aperture in front of the film.

I prefer, however, as an aid to the operator in centering the light rays upon the film to employ a slit back of the film, i. e., between the light source and film. This slit, however, is relatively wide, six mils, for example, as compared with the one mil aperture or slit now used.

In the drawing:

Fig. 1 illustrates diagrammatically one embodiment of my invention;

Fig. 2 is a modification;

Fig. 3 is a further modification; and

Fig. 4 a still further modified embodiment of my invention.

Referring first of all to the embodiment of my invention illustrated in Fig. 1: 1 designates a light source of constant intensity. This light source may be of the same type as those now employed using either a coil or a ribbon filament. 2 designates a lens system embodying as is customary a condensing lens system 3, and objective lens system 4 intermediate the light source and film. 5 is the film on which the sound to be reproduced has been photographed, the frequency images on this film being of varying degrees of intensity, varying with the original sound recorded.

6 illustrates diagrammatically a photoelectric cell or light sensitive electric device which it will be understood is connected electrically in the usual way to an amplifier and loud speaker, not shown. The cell, amplifier and loud speaker may be of usual construction.

Prior to my invention, in an installation of this character, a one mil light slit would be employed intermediate the condensing lens system 3 and the objective lens system 4, the light rays from the light source 1 being focused by the projectionist upon this slit so that the image of the slit is focused upon the film, the light rays then passing through the slit and through the film and falling upon the surface or window of the photoelectric cell 6. By the present invention, however, I have eliminated the necessity for the narrow slit just mentioned with its inherent drawbacks above referred to and provide a highly restricted, minute circular aperture. in front of the film 5 intermediate it and the photoelectric cell 6. The aperture plate in which the aperture or apertures are provided is designated'l, and as will be seen from the drawings is located in close proximity to the film.

I have found by a great many tests that no particular skill is required on the part of the projectionist to direct the lightrays from the light source 1 upon the film 5 in such a manner that the light rays will pass through this film and through the pinhole aperture '7 to the photoelectric cell 6. I find also that any sagging of the filamentof the light source met with in practice is not detrimental, the light rays despite such sagging striking the film 5 to pass therethrough and from thence through the aperture or apertures 7'.

I have found also that by the use of the aperture or apertures 7' I am enabled to obtain a better concentration of the light rays upon the aperture 7 to the cell, so that an increase is obtained in the cell emission as compared with present practice. 7

whether or not the same has sagged, inasmuch I have found also that inasmuch as the aperture 7' is so highly restricted as to be extremely minute overlapping of frequency images projected upon the photoelectric cell is avoided with the result that reproduction is ideally clear.

As above mentioned I have found also that comparing my system with prior systems, taking a given power input, there is a marked relative increase in output with my system. This is apparently due to the increased pressure on the photoelectric cell produced by the concentrated light rays passing through the highly restricted aperture 7' placed in front of the film as distinguished from the use of a one mil slit behind the film.

In Fig. 2 I have shown a slightly modified embodiment of my invention in that I have provided a mechanical slit 8 intermediate the two lens systems 3 and 4. This slit or aperture 8 is employed merely as a convenient means of facilitating directing of the light rays from the light source 1 upon the film 5 in line with the pinhole aperture '7'. In other words, it will make the work of the projectionist easier in centering his light.

In Fig. 3 I have employed the apparatus of Fig. 2, and in addition I have provided a lens system 9 between the aperture '7' and the photoelectric cell. This lens system 9 enables me to project a sharper image on the face of the photoelectric cell 6 than where this lens system is omitted.

In Fig. 4 the apparatus employed is similar to that of Fig. 3 except that in this instance I have protected the aperture '7 against dust or other foreign materials by enclosing the same in the tube of the lens system 9, the aperture being located in this tube intermediate the two lenses of this system which-have been designated 10 and 11, respectively.

It will be appreciated from all of the foregoing that my invention provides for the interposition of a very highly restricted aperture intermediate the sound film and light sensitive electrical device, the aperture being so located with respect to the film that light rays passing through the film and aperture are concentrated upon the surface of the electrical device, thereby insuring desired intensity of reproduction without increase in power input.

It will be appreciated also that the nature and location of the aperture employed are such that overlapping of frequency images upon the light sensitive electric device is avoided.

, It will be seen also that inasmuch as the aperture or apertures 7 employed by me are so highly restricted in area, such apertures lend themselves for use in connection with sound records much less in width than standard records, .thereby adapting my invention for use in connection with sound motion picture projectors for home use, where the apparatus is necessarily simplified as compared with the apparatus used by professionals, and wherein a reduction in the width of the sound track would be of great advantage.

What I claim is:-

1. In an apparatus for reproducing sound from a variable density sound film, the combination of a light source behind the film, a photoelectric cell in front of the film, and an aperture plate having a pinhole aperture intermediate the cell and film. I

2. In an apparatus for reproducing sound from a variable density sound film, the combination of a light source behind the film, a photoelectric cell LOO in front of the film, an aperture plate having a pinhole aperture in front of the film intermediate the cell and film, and a condensing and objective lens system behind the film intermediate the film and light source.

3. In an apparatus for reproducing sound from a variable density sound film, the combination of a light source behind the film, a condensing lens and an objective lens and an intermediate light slit behind the film intermediate the film and light source, a photoelectric cell in front of the film, and an aperture plate having a pinhole aperture intermediate the cell and film.

4. In an apparatus for reproducing sound from a variable density sound film, the combination of a light source behind the film, a photoelectric cell in front of the film, an aperture plate having a pinhole aperture in front of and adjacent to the film and intermediate the cell and film, and an objective lens system intermediate the aperture plate and cell.

5. In an appaartus for reproducing sound from a variable density sound film, the combination of a light source behind the film, a photoelectric cell in front of the film, a lens tube intermediate the film and cell, lenses in said tube, and an aperture plate having a pinhole aperture located in said tube intermediate said lenses.

6. In an apparatus for reproducing sound the combination of a sound film carrying variable density sound images, a light source of fixed intensity behind the film, a photoelectric cell in front of the film, and an aperture plate intermediate the said cell and film and in the path of the light rays passing through said film from said light source, said plate being provided with a pinhole aperture so restricting the light rays passing from the light source through the film to said photoelectric cell that the projection of overlapping sound images on the photoelectric cell is avoided.

7. In an apparatus for reproducing sound, the combination of a sound film carrying variable density sound images, a light source of fixed intensity behind the film, a condensing and objective lens system intermediate said film and light source, a photoelectric cell infront of the film, an aperture plate intermediate the said cell and film and in the path of the light rays passing through said film from said light source, said plate being provided with a pinhole aperture restricting the light rays passing to the photoelectric cell at any instant to a single sound image.

8. In an apparatus for reproducing sound, the combination of a sound film carrying variable density sound images, a light source of fixed intensity behind the film, a condensing lens and an objective lens and an intermediate light slit behind the film intermediate it and the light source, a photoelectric cell in front of the film, and an aperture plate intermediate the said cell and film and in the path of the light rays passing through said film from said light source, said plate being provided with a pinhole aperture so to restrict the light rays passing from the light source through said film to the photoelectric cell that the projection of overlapping sound images on the photoelectric cell is prevented.

9. In an apparatus for reproducing sound, the combination of a sound film carrying variable density sound images, a light source of fixed intensity behind the film, a photoelectric cell in front of the film, an aperture plate intermediate the said slit and film and in the path of the light rays passing through said film from said light source, said plate being provided with a pinhole aperture so restricting the light rays passing from the light source through the film to said photoelectric cell that the projection of overlapping sound images on the photoelectric cell is avoided, and an'objective lens system intermediate said aperture plate and cell.

10. In an apparatus for reproducing sound, the combination of a sound film carrying variable density sound images, a light source of fixed intensity behind the film, a photoelectric cell in front of the film, a lens tube intermediate the film and cell, lenses in said tube, and an aperture plate located in said tube intermediate said lenses and intermediate the said cell and film and in the path of the light rays passing through said film from said light source, said plate being provided with a pinhole aperture restricting the light rays passing to the photoelectric cell at any instant to a single sound image.

JOSEPH SHAW.

CERTIFICATE OF CORRECTION.

Patent No. 1,939,726. December 19, 1933,

JOSEPH SHAW.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, beginning with line 142, strike out all to and including line 28, page 3, comprising claims 1 to 5 inclusive; and the claims appearing in the patent as numbers 5 'Z, 8, 9, and 10, should bear the numbers i, 2, 3, 4, and 5 respectively; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 30th day of January, A. D. 1934.

F. M. Hopkins (Seal) Acting Commissiener oi Patents

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