US2205513A - Process and device for the reproduction of fixed density sound records - Google Patents

Description

9 R. BERNHEIM 05,51

. n I raocnss AND nfivmn FOR THE marnonuc'nofi 0F FIXED DENSITY somm macqnns Filed lay 24; 1937 2 s eets-sheet m/mrm ROGER BERNHEIM By w/95 PatentecPJime 1940 UNITED STATES PROCESS AND DUC'IION RECORDS pnvrcr: Foa 'rnn macor FIXED DENSITY scum) Roger Bernheim, Paris, France, assignor to Socit Oinoza, Socit Anonyme, Paris, France, a corporation or France Application May 24, 1937, Serial No. 144,535

Y In France May 29, 1936 3 Claims. -(Cl. nil-i003).

Fixed density sound records are substantially produced according. to two difierent methods. According to a first method, which is the older,

- the sound track is divided into two equal parts, 5 one transparent and the otheropaque, during the periods of silence. During the periods of singing or conversation, elongations are recorded on either side of the axis of the track with an equal intensity, as shown in Figure 1 of the ac- 1'0 companying drawings.

When such'a track is being translated into sound by passage across a luminous slit of constant length, the slit, during the periods of silence, allows a light band corresponding. to half its length to pass to the photo-electric cell, which produces'a very unpleasant background noise.

, According to the second method, shown in Figure 2, the track is substantially the same but it isenveloped by a black part which fills the transparent zone of Figure 1 as completely as possible.

This is the arrangement called noiseless which considerably reduces the background-noises during the silences or zones of weak modulation, in

V consequence of the suppression of a large part of the light from the slit which fell uselessly on the photo-electric cell in theprevious case.

There are other sound tracks derived from the preceding tracks and possessing the same properties, but for clearness of the description, only the types according to Figures 1 and'2 will be considered, without limiting the invention only to this form of fixed density recording.

The process to be described makes it possible substantially to translate non-noiseless filn'i by means of a luminous slit, the length of which is constantly reduced to the mean value of the elongations of the sound track.

The present invention makes it possible to eftect noiseless reproduction starting from. 8. rec- 0rd of the type shown in Figure 1 without altering its appearance and without employing mechanical or electro-'-mechanical devices actuated in the course of operation, directly or indirectly,

. by the modulation recorded on the film, the invention employing a method of invariable illu-fl mination adjusted once and for all, which will be described hereinafter. V I

0n the sound track of a sound film, the support of which is transparent, there is projected a bright light so as to illuminate 'a rectangle ABCD, Fig. 3, having a length AB equal to the length of a cyclecorrespondlng to a sound of lower pitch than the lowest sound which the amplifier and loudspeaker are able to render. It 56 101' example this latter sound'corresponds to cycles. if therecord has been made at a speed of 0.32 meter per second, and ifthetrack is 2 mm. wide, it will be illuminated with a luminous rectangle 6 mm. long and 2.5 mm. wide. It is assumed that the sound track is bordered with 6 black on both sides. The luminous fiux passing through the sound track during the passage of a portion modulated at constant amplitude practically does not vary in each of the halves of the rectangle separated by the axis of the record. 10

The pencilof rays which has traversed the film is reutilized to form the image of. the rectangle ABCD (Fig. 3) at. A'BC'D' in such a manner that the point A forms its image at A, B at B,

C at C and D at D, the line'BC being substan- 15 tially coincident withv the line B'C'. Assuming the area of the luminous rectangle decomposed into elemental rectangles abc'd' and a b c d parallel to the base AB. it will be seen that each of these rectangles form its imagea'laZa'iia't 20 and a2b'2c'2d'2 on a corresponding zone of the rectangle A'B'C'D'. it being possible to consider the center of BC as the center of symmetry. If the modulation is assumedto be substantially 'constant as to amplitude, it will be seen that all as mentary rectangles outside the modulation in 35 its transparent portion and in its opaque portion will not allow light 'to pass, either because they do not receive any in the transparent portion or because they stop that which falls in the opaque portion. Light will therefore only be passed 40 through the elementary rectangles corresponding to the 'width of modulation. If, in particular, the, modulation is zero, no light will pass through the rectangle-A'B'C'D'.

A film thus illuminated, however, may give 5 rise to sound interference or beats due to superposing of the two translations, and this can be overcome by projecting the modulation of the rectangleABCD while diflusing it in the longi-. tudinal direction that is, the direction of film 50 movement, as hereinafter described.

Instead of eifecting the translation by means of a mechanical slit placed at E'F', it is possible to employ a projection translation device, that is to say to project through an objective the u portion of the film adjacent E'F', so as to form a distinct image thereof on a mechanical slit 0! suitable width behind which is situated the photo-electric cell; The objective may'lurthermore be replaced by a concave metal mirror producing the sameefiect.

A constructional form of apparatus according to the invention is shown in Figure 4 of the accompanying drawings. i is the filament or an incandescent-lamp producing by means oi. the condenser or objective 2 an'image outlined along 3-4, its center being at 5 on the optical a'xls of the condenser. A concave mirror 8, the center of curvature of which is at I and the radius of curvature of which is determined by the point of intersection i of the normal to the film at! with the optical axis of the condenser reproduces the image 3-5-1 at'3'-'-l', the points 4 and i coinciding. At 8 is a grooved transparent plate, and 9 is an objective lens assembly having two groups of lenses iii and ii which project an image of the portion 0! the film adjacent 5' on to the mechanical slit l2, behind which is a photo-electric cell ii of the barrier layer type, the distance of which from the optical system being adapted to the dimensions of the cell.

Fig. 4 shows by cross-hatching how the pencil of rays starting from the point 5 and reflected at the mirror "5 is difiused by the plate I over the space 5a-5b. The film M moves over rollers i5 and I6 which may iurthermore be replaced by any equivalent device adapted to the nature of Fig. 5 shows a non-noiseless record produced on a black coating deposited on the surface or a transparent film by growing by means 01 a graving tool having a rectilinear edge moving transversely. It is possible to apply the invention to a record of this kind by supposing the width or the track to be divided into two equal portions u and b, each of which is regarded as a-normal non-noiseless trash on which the above-described light deviceis allowed to act. 0n the other hand, since each trash c and h gives oppomte chests,

they will be arranged in a push-pull connection having a double photo-electric cell which will enable the two eilects to be added together instead of being cancelled.

The invention described makes it possible to produce directly on sensitised films noiseless copies starting from a non-noiseless record. For this purpose, it is merely necessary to cause a sensitive film to move in contact with the mechanical slit which, in the foregoing description, has been assumed to be placed at ET.

I claim:

1. A method for the acoustic reproduction of fixed density sound tracks on films, which comprises illuminating intensely a certain length of the sound track and redirecting the luminous flux falling on each of the half-widths of said track length onto each of the halt-widths of an adjacent track length while inverting the redirected luminous flux so that the modulated portion of the second track length receives exclusively the light which has passed through the modulated portion of the track length that has received direct illumination, and diffusing the redirected luminous flux exclusively longitudinally of the film before it reaches the second length of the track.

2. A device for theacoustlc reproduction of fixed density sound tracks on films. comprising a light source, an optical system for forming a rectangular image of the light source on a determined length of the sound track, a reflecting system for projecting said image onto an adjacent length of the sound track, means interposed in the path of the beam of light between the two illuminated track lengths for diflfusing the said beam in the direction of film travel, and an optical system for projecting onto a photo-electric cell the image projected onto the second length of the track.

3. A method of sound reproduction from a constant densitysound track film, comprising disuch a manner' that the modulated portion of the second track length receives only the light that has traversed the directly illuminated first track length, and diffusing the redirected luminous flux in the direction of longitudinal movement of the sound track before saidfiux falls on said second track length and without modifying said luminous flux in the transverse directlon.

- ROGER BERNHEHE.

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