US1552926A

US1552926A - Photo-electric means for reproducing sound from graphical records

Info

Publication number: US1552926A
Application number: US747313A
Authority: US
Inventors: Hart Russell
Original assignee: Individual
Current assignee: Individual
Priority date: 1924-11-01
Filing date: 1924-11-01
Publication date: 1925-09-08
Anticipated expiration: 1942-09-08

Description

Sept. 8, 1925. 1,552,926

R. HART PHOTO-ELECTRIC MEANS FOR REPRODUCING- SOUND FROM GRAPHICAL RECORDS.

Filed Nov. 1. 1924 i l l i l l l h i lfi Yrs" Inventor,- l'ZuSseZZ .Zi'art .fmm

.Attorriey.

Patented Sept. 8, 1925.

RUSSELL HART, OF LOS ANGELES, CALIFORNIA.

PHOTO-ELECTRIC MEANS FOR REPRODUCING SOUND FROM GRAPHICAL REtJOBDS.

Application filed November 1, 1924. Serial No. 747,313.

To all whom it may concern I v Be it known that I, RUSSELL HART, a citizen of the United States, residing at Los Angeles, in the county of Los Angeles and State of California, have invented a new and useful Photo-Electric Means for Reproducing Sound from Graphical Records, of which a specification is set forth below. I 1

In this specification, and the accompanying drawing, Ishall describe and show a preferred form of my invention, and specifically mention certain of its more important objects. I do not limit myself to the forms disclosed, since various changes and adaptations may be made therein without departing from the essence of my invention as hereinafter claimed; and objects and advantages, other than those specifically mentioned, are included within its scope.

My invention relates to photo-electric means for reproducing sound from graphical sound records' In a general way its object is to improve the quality or fineness of sound reproduction so that, if the record truly represents the original soundin quality, the reproduction will be true in quality also.

More specifically my principal objects are; first, to provide sound reproducing means adapted to respond to exceedin ly small variations in graphical sound recor 8; second, to furnish facilities for obtaining the full effect of the recorded overtones in the reproduction so that the quality of the reproduced sound will correspond very closely to the original; third, to obviate the effect of stray noises in the reproduction due to mechanical vibrations; and, fourth, to secure the above results by means of a paratus of great simplicity and relative y lo'w'cost,

My invention is particularly adapted for the reproduction of sound from photographic film records, but may be used also for reproducing from other graphical sound records. I prefer to use a photographic film record of substantially constant density and variable width, but a film having a record thereon of uniform width and varying density may be used,with practically equal facility.

The objects of the invention are attained in the manner illustrated in the accompanying drawing, in which- Figure'l is a diagram showing a typical arrangement of my apparatus for reproduclng sound from a photographic film rec- Figure 2 is a front elevation of a portion of aphotographic film with a sound record thereon; and a .gate through which it is made to slide, and by which it is definitely positioned;

' Figure 3 is'a longitudinal section of the above gate and film; and a side elevation of a preferred type of photo-electric cell attached to thegate at the rear;

Figure 4 is a rear sectional elevation of the above cell;

Figure 5 is aside elevation of a preferred type of incandescent lamp I usev as a primary light source in my apparatus; and

Figure 6 is a diagram, greatly enlarged and exaggerated,to illustrate the manner in which reflection of the light from the primary source may be utilized for obtainmg a much attenuated image thereof for. use as a secondary source which is directly employed for the reproduction of sound.

Similar reference numerals refer to similar partsthroughout the several views.

In apparatus of this general character,

,wherein a luminous rectilinear filament is employed as a source of light, it has hitherto been the effort to makeuse of a very tenuous filament in order to have the re ro- 4 duction as free as possible from the e ects of blurring inevitably accompanying the use of a wide band of light. I have found that the light emanating from tenuous incandescent filaments is very "far from constant as the result of unavoidable vibration,

and that this causes a distortion of the re? produced sound quite as objectionable as the blurring. It is believed that the changes in light emanation in such filaments, when subjected to vibration, is due to changes in the electrical conductivity resulting from variations in tension caused by the vibration; and I have found that relatively stout filaments do not give this trouble.

In my apparatus, therefore, I employ for the primary light source an incandescent.

lamp 7 having a relatively thick and strong rectilinearfilament 8, not appreciably-affected in light emanation by mechanical vibrations. I mount this lamp adjustably on a stand 9, which also adj ustablv supports a small cylindrical mirror 10 serving as a secondary light source for the reproduction of sound. a

It is well known that an object reflected from a cylindrical mirror appears to be greatly attenuated in the direction of the axis of the mirror, and that this effect hecomes more marked as the radius of the cylindrical surface is decreased. This effect is diagrammatically illustrated in Figintrinsic brilliancy thus becomes available. for sound reproduction by photo-electric.

means.

As illustrated, the soundrecord 13 consists of a photo-exposed and developed area of substantially uniform. density and very much varying width, appearing as a relatively narrow longitudinal band parallel to,

* and near one edge of, a motion picture film 14. It is usually p'referable'to have the outer edge 15 of this record rectilinear, and

- this edge may then be considered to represent the axis of abscissae of a very irregular curve 13 corresponding to the recorded sound wave. The ordinates of the curve represent volume of sound, or loudness, and the distance between peaks, or correspond.- ing points on the curve, correspond to p1tch. The overtones and fundamentals of the recorded sound determine the shape of curve 13. I

In prior applications for United States patents (No. 608,499 filed Dec. 22, 1922 and No. 630,870 filed April 9, 1923) I have shown and described means for producing such sound records as above described upon uniformly moving photographic films. The recording process therefore need not be described herein.

For reproducing purposes the type of photographic film record described, or a similarly produced type having a record of uniform width and varying density, is made to travel at the recording speed through a gate 16. This may be accomplished by driving the film sprocket 17 by means of a motor 18, the film being unwound from reel 19 and re-wound upon reel 20. Figure 1, being diagrammatic rather than pictorial, does not illustrate the mechanism by which reel 20 is driven to accomplish the re-winding. Such means, however, are well known to those familiar with the motion picture and allied arts.

The approved form of sound gate illustratedv comprises a fixed plate 21, having a hinged cover 22, and two pairs of polished raised

runners

23 and 24 between which the Runners 23 are fixed or made integral with plate'21, and runners 24 are pressed inwardly from cover 22 by springs 26 guided by studs 27.

- Cover plate 22 is provided with a small rectangular aperture 28, and there is a similar aperture 29 in the rear plate of the gate. Behind the latter aperture'is mounted a suitable, highly sensitive, photo-electric cell 30. 1

The type of photo-cell here shown comprises a very fine platinum grid 31 filled with selenium or other photo-active material, on a glass or quartz cover plate 32, and connected by platinized strips-33 to terminal wires 34. A cup 35 containing anhydrous calcium chloride is .sealed upon the cover plate enclosing the photo-active ma' terial and grid.

A process for making an exceedingly sensitive and rapid photo-electric cell of the above described type has been fully described in United States Patent No. 1,491,- 040, issued to me on April 22, 1924:.

In operation my reproducing apparatus is assembled in the manner indicated in Figure 1 with a lens system 36 intermediate cylindrical mirror 10 and gate 16. By means 'ofthese lenses a sharp secondary image of the mirrored image of the luminous filament is focused upon the sound record of the film. This brightly illuminates an exceedingly narrow transverse band of the record, and the light rays that pass through the film are variably modulated thereby and impinge upon the photo-electric grid 31. This constantly varying light flux will proportionately vary the electrical resistance of the photo-active material in the grid, and thus make it possible to reproduce the original sound by telephonic means.

There are various well known means for amplifying a small electric current, modulated by the action of a photo-electric 'cell, to make it available for operating loudspeaking devices. One method of domg this is illustrated diagrammatically in Figure 1, wherein certain standard electrical devices are conventionally shown. In this diagram a loud-speaking instrument is indicated at 37, an audion at 38, a variable ratio transformer at 39, a variable resistance at lO, and a condenser'at 11. The diagram shows a satisfactory manner {for connecting these devices to batteries 42 and 43, with the photo-electric-cell 30 in circuit in the system. i

The use of quartz for plate 32, upon which the photo-active material ofthe cell is deposited, is desirable on' account of the optical.

may be. eliminated in the above described manner. Also that, b reason of the exceedingly thin band 0 light falling upon the'film, there is practically no blurring of the reproduced sound due to overlapping p the efiects of adjacent portions of the sound record.

Having thus fully described. my invention, I claim: c

11. Photo-electric sound reproducing means comprising; a movable optical film with a sound record thereon adapted for variably intercepting light rays; a linear light source; and a cylindrical mirror whereby an attenuated image of said source may be thrown upon said record.

2. Photo-electric sound reproducing means comprising; a movable optical film with a sound record thereon adapted for variably intercepting light rays; a linear light source; a cylindrical mirror whereby an attenuated image of said source may be thrown upon said record; and a photo-electric cell behind the record adapted for modulating. an electric current by the rays transmitted by said record. w

v 3. Photo-electric sound reproducing means comprising; a movable optical film. with a sound record thereon adapted for variably intercepting light rays; a linear light source; a cylindrical m rror adaptedfor reflecting an, attenuated image of said source;

and a lens intermediate said mirror and said record whereby reflected light rays from the former may be focused upon the latter.

4. Photo-electric sound reproducing means comprising; a movable optical film with a sound record thereon adapted for variably intercepting light rays; a linear light source; a cylindrical mirror. adapted for re fleeting an attenuated image of saidsource;

a lens intermediate said mirror and said I record whereby reflected light rays from the former may befocused upon the latter; and a photo-electric cell behind the record adapt ed for modulatin an electric current by the rays transmitted y said record.

5. Photo-electric sound reproducing rneans comprising the elements set forth in claim 4 in combination with; means for passing an' electric current through said cell for modulat-ion thereby; and means for utilizing said modulated current for the reproduction/of sound. e 6. Photo-electric sound reproducing means comprising the elements set forth in claim 4 in combination with; means for passing anelectric current through said cell for modulationthereby; and means for amplifying and telephomcally utilizing said modulated current for the reproduction of sound.

; RUSSELL HART.