US1794513A

US1794513A - Electromagnetic light-modulating device

Info

Publication number: US1794513A
Application number: US424839A
Authority: US
Inventors: Olindo O Ceccarini
Original assignee: METROGOLDWYN MAYER CORP
Current assignee: METROGOLDWYN MAYER CORP; METROGOLDWYN-MAYER Corp
Priority date: 1930-01-31
Filing date: 1930-01-31
Publication date: 1931-03-03
Anticipated expiration: 1948-03-03

Description

March 3, 1931. O O CECCARINI 1,794,513

ELECTROMAGNETIC LIGHT MODULATING DEVICE Filed Jan. 31, 1930 2 Sheets-Sheet l swam dot 0Za 22d0 0 (6064/2528 Patented Mar. 3, 1931 UNITED STATES PATENT OFFICE OLINDO O. GECOARINI, OF BEVERLY HILLS, CALIFORNIA, ASSIGNOR T METRO- GOLDWYN-MAYER CORPORATION, OF CULVER CITY, CALIFORNIA, A CORPORATION OF NEW YORK ELECTROMAGNETIC LIGHT-MODULATING DEVICE Application filed January 31, 1980.. Serial No. 424,839.

This invention relates to an electromagnetic light valve adapted tobe employed in modulating light during photographic recording of sound. The invention particular- 6 1y relates to a light valve of sturdy construe tion which has a natural period of frequency incapable of producing annoying audible sounds, and which maintains its spacing position and mechanical characteristics without 10 impairment under strenuous working conditions.

Heretofore, light valves employed in sound recording generally consisted of an armature carrying a pole piece having a minute slot therein, the armature carrying bridge members over which a thin metallic loop was stretched, a portion of the loop comprising two parallel ribbon portions in spaced relation. The slot in the armature is generally about eight mils wide by 256 mils long. The metallic ribbon or tape is only 6 mils wide and 0.3 mils thick, the two ortions of the loop being spaced so as to mm a slit 2 mils wide. A single electromagnetic coil was employed.

The minute metallic ribbons used in valves of the ,prior art necessitated extreme care in setting, and very often under the influence of oscillatory currents of high amplitude, the ribbons were displaced relatively to each other so that the opening therebetween was changed from the customary opening to an opening of smaller or greater width. If one or both of the ribbons had been shifted so as to widen the slit, then the quantity of light passing through the valve in the unmodulated condition became greater, thereby materially affecting the distinctness and volume of the record produced.

- An object of this invention is to disclose and provide an electromagnetic light valve in which relatively heavy strips are employed without decreasing the operating range of the valve.

Another object is to disclose and provide a light valve assembly which permits ready adjustment.

A still further object is to disclose and provide an electromagnetic light valve in which the light modulating elements are activated described, but embraces all such changes and by flux variations of an electromagnetic circult, without passing a current through the light modulating elements.

Another object is to disclose and provide a sturdy light valve construction which may be. readily transported, moved or shifted and which is not crltically sensitive to tempera ture changes. i

A still further object is to disclose and provide a light valve which may be employed in the pro notion of variable area or variable density sound records.

A still further object is to disclose and provide an electromagnetic light valve in which a vibratory element is caused to vibrate under the influence of a magnetic flux which is varied by the oscillatory current which it is desired to record.

Other objects, uses and advantages of this invention will become apparent to those skilled in the art from the following detailed description of one preferred form of the apparatus, it being understood that the invention is not limited to the device specifically modifications as come within the skill of the art.

In describing the illustrative form of this invention, reference will be had to the appended drawings, in which:

Fig. 1 is a diagrammatic representation of an arrangement of elements employed during the recording of sound, on a continuous film.

Fig. 2 is an enlarged side elevation of one form of electromagnetic light valve.

. Fig. 3 is a plan view of the light valveshown in Fig. 2. V

Fig. 4 is an end elevation, partly in section, of the light valve shown in Figs. 2 and 3, the section being taken along line 44 of Fig. 2.

Fig. 5 is a longitudinal section taken along line 5-5 of Fig. 3.

As shown in Fig. 1, the sound recording 95 equipment may comprise a fixed light source 1, a condensing lens system 2, a light modulating device 3 provided with a fixed slot through which the light is passed, an'ob ective lens system' i, and means 5 for passmg'a 1.00

continuous film 6 thereby, upon which the light modulated by the device 3 is recorded.

The light modulating device embraced by this invention is illustrated in Figs. 2 to 5 inclusive, and preferably comprises a yoke 7 provided with a suitable surface 8 adapted to seat upon a stationary base having a predetermined relation with the light source lens systems and film movi device 5. The yoke 7 is preferably provide with outwardly extending flan s 9 adapted to receive and support the lock assembly, generally indicated at 10. Theyoke 7 may also include a bracket 11 provided with a lens receiving member 12, said lens receiving member 12 being adapted to receive the condenser lens 2.

The block assembly preferably comprises-twoopposed recessed blocks 13 and 13'. Blocks 13 and 13' are preferably provided with recesses 14 communicating. with a smaller aperture 15, said smaller apertures facing each other in the block assembly. The opposing upper and lower faces of the

blocks

13 and 13 ma also be provided with recesses 16 and 17. The partitions 18 dividing recess 15 fromi the recesses 16 and 17 are preferably curved as indicated at19 so as to form a curved rest for a strip of magnetic material 20. These strips of magnetic material 20 are preferably held in a clamp member such as the member 21, provided with an upper serrated surface 22,. a clamp pad 23 being provided having a similar serrated surface. The clamp pad 23 may be held in firm contact with the clamp member 21 in any suitable manner, such as for example, by means of a screw 24.

The clamp member 21 may be provided with a curved or semi-cylindrical rotuberance 25 adapted to be received in a c amp seat 26 keyed into or formed in the block 13 and preferably in the portion 18 of the block 13. The clamp member 21 may be adjustably positioned by means of a screw 27 threadedly mounted in a support28 firmly held by or attached to the block 13. Inasmuch as the clam members 21 are in the form of'a bell cran lever pivoting at 25, the tension in the strips of ma etic material 20 may be adjusted to a nicety by regulating the screw 27 which rests upon the surface of one of the legs of the clamp 21. X

The recess 14 of the blocks 13 is adapted to receive an exciting coil 30, said coil being provided with a core 31. Preferably, the core 31 has its axis parallel to the longitudinal axis of the strip of magnetic material 20.

Core members

32 and 33 are preferably connected to the ends of the core 31, said core members extending through the aperture 15 in the block 13. The

core members

32 and 33, during a portion of their length, are preferably parallel to each other, as for example the portions 32' and 33' in the port 15. The

core members

32 and 33 prefera ly terminate in close proximity to each other so as to form a gap indicated at 34. The ends of the

coremembers

32 and 33 preferably approach, but do not protrude beyond the plane connectin the outermost edges of the portions 18 of t e block 13. In other words, they do not contact with, but are merely in close proximity to the strips of magnetic material 20. 7

Voice

current coils

35 and 36 are carried by the core members-32 and 33, and are preferabl positioned around the parallel core

mem er portions

32 and 33. These voice

current coils

35 and 36 may be either connected in series or parallel, but in such direction as to produce an additive efi'ect insofar as magnetic flux is concerned. Oscillatory current from suitable amplifiers, which in turn are supplied with current from microphones, is sent through these voice coils. The space between the ends of the

core members

32 and 33, and particularly the outer surface of the voice

current coils

35 and 36, may be covered by a plate 37 of non-magnetic insulating material such as for example, a phenol condensation product.

The block members 13 are preferably con-- nected together in spaced relation and means are provided for adjustably positioning the bloc s 13 and 13' in such spaced relation. Such means may comprise connecting

plates

40 and 41, the plate 40 being connected to the block 13, whereas the plate 41 is connected to the block 13. The

plates

40 and 41 may be connected to their respective blocks in any suitable manner, as for example, by means of screws 42. It is to be understood that a similar set of

plates

40 and 41 is connected to the upper surfaces of the

blocks

13 and 13 as well as to the lower surfaces.

The

plates

40 and 41 are preferably provided with ofi-

set portions

43 and 44, respectively, adapted to come in sliding contact with each other, the portion 44 fitting into a dove-tail roove 45 formed in the portion 43. Minor adjustments between the

plates

40 and 41, and therefore,.between the

portions

43 and 44 may be made b means. of a suitable headless screw 46 a apted to come into threaded engagement with an internally threaded aperture 47in the member 44, the screw 46 being rotatably connected to but longitudinally immovable in the member 43.

The screw 46 may be rotatably held in the member 43 by means of a plurality of screws 48 provided with smooth cylindrical ends of smaller diameter than said screw 48, said I ably held together by means of interlocking

plates

40 and 41. -This block assembly as a unit may then be mounted in the yoke 7 as follows.

End plates and 51 adapted to contact with the outer surfaces of the blocks 13 and with the inner surfaces of the interlocking

plates

40 and 41 are provided. Said plates may be connected to the blocks 13 by means of suitable screws 52, and may also be connected to the upper and lower interlocking.

plates

40 and 41 by means of screws 53. The

end plates

50 and 51 are preferably provided with flanges 54, each of said flanges being provided with a slot 55, said flanges 54 being adapted to rest on the flanges 9 of the yoke 7.

The

end plates

50 and 51 may then be connected to the yoke 7 by means of bolts 56 passing through the slots 55 in the flanges 54 of the end plates5O and 51, the bolts 56 coming into threaded engagement with the flanges 9 of the yoke 7 as indicated at 57. The block assembly may then be adjustably positioned with reference to the yoke (while said bolts 56 are still loose) by means of set screws 58 at right angles to the bolts 56, said set screws 58 passing through the flanges 9 of the yoke 7 and contacting with the outer surfaces of the

end plates

50 and 51.

In order to facilitate the adjustment of

plate

40 and 41 relatively to each other, an aperture 59 may be provided in the yoke 7 said aperture being in alinement with the longitudinalaxis of the adjustment screw 46, thereby permitting the insertion of a suitable implement for the manipulation of the adjustmentscrew. Similarly, an aperture 60 may be formed in the base 8 of the yoke, said aperture being in alinement with the set screw 49.

It is to be understood that suitable binding posts, such as the binding posts 61 and 62,

are provided, said binding posts permitting electrical connections to be made with the exciting coils 30 and with the voice coils 35 and 36. The voice coils are preferably connected in series. 7 j

While a. predetermined current is passed through the exciting coils 30, the strips of magnetic material 20 are placed under tension by suitable manipulation of the adjusting screws 27. The tension should be suflicient to definitely prevent the strips of magnetic material 20 from contacting with the ends of

core members

32 and 33 under the influence of the greatest flux concentration which the mechanism may be subjected to, but insuflicient to prevent the strip of magnetic material 20 from being afiected by variations in the flux. In other words, the strip 20 should be movable toward or away from the ends of

core members

32 and 33 under the influence of variations in the flux, thereby changing the effective gap between the ends of

core members

32 and 33 and changing the reluctance of the magnetic circuit.

When a voice current is passed through the voice current coils 35 and 36, the quantity of flux across the gap will be varied, thereby either drawing the magnetic strip 20 closer to the ends of the

core members

32 and 33, or permitting the tension. of the magnetic strip 20 to withdraw'the strip from the ends of the core members. In this manner the strips of magnetic material 20 may be caused to vibrate toward and away from the ends of the

core members

32 and 33, said vibrations being synchronous with the changes in the current passing through the voice coils, the amplitude of the vibrations of the magnetic stripsQO being regulated by the amplitude of the voice current. V,

The strips of magnetic material 20 are preferably provided with masking means 63, said masking means being carried by each of the magnetic members 20 and extending substantially at right angles to the plane of the magnetic strips 20. Furthermore, the mask 'ing means 63 should preferably lie in substantially the same plane and each of said masking means should be preferably provided with a true, smooth and sharp edge. The distance between the edges of the masking means 63 may be varied, depending upon the size of the slit or opening through which the fully modulated light will pass. The inner edges of the masking members 63 influence either the width or the length of the slot, thereby graduating or modulating the total quantity of light passing through the slit and being impressed upon the continuous film or other substance receiving the record of the voice current.

If, {or example, the fixed slit has its longitudinal axis lying in the horizontal planet whereas the boundaries or adjoining edges of the masking means 63 are vertical, a record of the double envelope type (variable area) may be produced. If only one of the strips of magnetic material 20 is caused to vibrate ormod ulate the light (as by deactivating the exciting coil and voice current coils in one of the blocks 13), then a variable area record of the single envelope type may be obtained.

If, however, the longitudinal axis'of the fixed slit is parallel to the adjoining inner edges of the masking members 63, then a variable density record may be produced.

The strips 20 are preferably made of spring steel or other magnetic material capable of being placed under appreciable tension, and having a high modulus of elasticity. Strips 20 need not necessarily be made of magnetic material, however, as the strips as a whole may be made of non-magnetic elastic material carrying targets such as the masking means 63 in those portions of the strip which :oppose the gap between the ends of the'core members.

It is to be understood that the voice current coils 35 and 36 and the exciting coils 30 are properly insulated from the blocks 13 and rigidly positioned in said blocks. In order to facilitate the positioning of the coils in the recesses of the block, members 64 may be provided, said members 64 being outwardly extending extensions of the

core members

32 and 33. These members 64 may then be attached or connected to the blocks 13 as by means of the screws 65. Furthermore, in order to conserve space, a recess 66 may be formed in the

end plates

50 and 51, said recess being adapted to receive the ends of the exciting coils 30.

It will thus be seen that an electromagnetic light valve has been provided, said valve consisting of two opposing recessed blocks, each of said blocks containing an'exciting coil and core members, said core members carrying voice current coils.

Furthermore, each of said blocks is provided with a strip of magnetic material lying in front of the gap formed between the ends of the core members. Means have been provided for clamping and placing the strips of magnetic material under tension.

Furthermore, means have been provided for adjustably positioning the block members relatively to each other, thereby permitting careful control as to the spacing of adjoining strips of magnetic material 20 or the distance separating the masking members 63. The invention has also provided for means for shifting the entire block assembly relatively to a yoke or relatively to a fixed slot or lens such as, for example, the lens carried by the extension 11 of the yoke 7. Although a specific form of apparatus has been described in detail, it is to be understood that the invention is not limited there- ,to. Numerous changes and modifications of design may be made by those skilled in the .in proximity to each other so as to form a gap, woice current coils mounted around each of said core members, a strip of magnetic material positioned in operative relation before the gap between the ends of each of said pair of core members, and means for placing said strip under longitudinal tension.

2. An electromagnetic light valve including two opposed exciting coils, spaced core members extending from said coils toward each other, the ends of said cores terminating in proximity to each other so as to form a gap, voice current coils mounted around each of said core members, a strip of magnetic material positioned in operative relation before the gap between the ends of each of said pair of core members, means for placing said strips under tension, and means for adjust ably positioning said coils and magnetic strips relatively to each other.

3. An electromagnetic light valve including two opposed exciting coils, spaced core members extending from said coils toward each other, the ends of said corps terminating in proximity to each other so as to form a gap, voice current coils mounted around each of said core members, a strip of magnetic material positioned in operative relation before the gap between the ends of each of said pair of core members, means for placing said strips under tension, means for adjustably positioning said coils and magneticstrips relatively to each other, and masking means carried by each of said magnetic strips, said masking means lying in the same plane and substantially at right angles to the plane of said magnetic strips, and-means for adjustably positioning said exciting coils and strips of magnetic material relatively to each other.

4. In an electromagnetic light valve, the combination of two opposing recessed blocks, an exciting coil positioned :in each of said blocks, a core in said exciting coil, core members connected to each end of said core, said core members terminating in proximity to each other so as to form a gap, voice current coils carried by said core members, a strip of magnetic material under tension carrie by each of said blocks, said strips passing immediately in front of the ga between the ends of said core members, an means connecting said blocks, said means including means for adjustably positioning said blocks relatively to each other.

5. An electromagnetic light valve comprising a yoke, a pair of opposed recessed blocks, means connecting said blocks, said means 1neluding means for adjustably positioning said blocks closer or farther apart so as to form a block assembly, means for connecting V said block assembly to said yoke including means for adjustably positionin said block assembly with res ect to said-yo e, an excit-" ing coil in each 0 said blocks, opposed core members extending from said coils toward each other, voice current coils 'mounted around said core members, a strip of magnetic material removably connected to each of said blocks and positioned in operative relation before the gap between the ends of said core members, means for placing said magnetic strips under tension, and masking means carried by each of said magnetic strips, said masking means lying in the same plane and siibstantially at right angles to the plane of said magnetic strips.

6. An electromagnetic lightvalve comprising two opposed recessed blocks, means for connecting and adjustably positioning said blocks relatively to each other so as to form a block assembly, a yoke, means for connecting said block assembly to said yoke including means for adj ustably positionin said block assembly with respect to said yo e, an exciting coil in each of said blocks, a core in each of said coils, core members connected to each end of said core, said core members for a portion of their length extending in parallel spaced relation at right an les to said core, and terminating in proximity to each other so as to form a gap, voice current coils carried by the parallel portions of said core members, a strip of magnetic material carried by each of said block members in operative relation before the gap between the ends of said core members, means for placing said strips of magnetic material under tension, and masking means carried by each of said magnetic strips, said masking means lying in the same plane and substantially at right angles to the plane of said magnetic strips.

7. An electromagnetic light valve includ-' ing an exciting coil, a core in said coil, said core being provided with ends terminating in proximity to each other so as to form a gap, voice current coils mounted around each of said core members, and a strip of elastic material positioned in operative relation before the gap between the ends of said core, said strip being provided with a magnetic portion carried thereby adapted to be actuated by variations in flux across said gap, and means for adjustably placing said strip of elastic material under a lon 'tudinal tension.

Signed at Culver City, alif., this 28 day of December, 1929.

' OLINDO O. CECCARINI.