Патент USA US2131293код для вставки
Sept. 27, 1938. ' 2,131,293 B. F. MltLER SOUND RECORDING 2 Sheets-Sheet l Filed July 5, 1935 3g 57 FIE_2_ Fumnw 4/4 INVENTOR BUQTON F M11. LEI? BY PEA ~ m1»? ATTORNEY Sept. 27, 1938. 2,131,293 B‘. F. MILLER SOUND RECORDING 2 Sheets-Sheet ‘2 Filed July 5, 1955 PIE. 5. “spar FB a INVENTOR. ' Bum-0N F M/LLEP BY A TTORN Patented Sept. 27, 1938 UNITED STATES PATENT OFFICE 2,131,293 SOUND‘ RECORDING Burton F. Miller, Hollywood, Calif., assignor to United Research Corporation, Long Island City, N. Y., a corporation of Delaware Application July 5, 1935, Serial No. 29,931 2 Claims. (01. 179-1003) This invention relates to sound translating de- taken along the line I—I of Fig. 2 and diagram vices and particularly to improvements in light matically showing the arrangement of an optical valves for use in recording sound by the varia- system associated therewith. ble area method upon a photographic medium. Fig. 2 is a sectional view taken along the line The invention is particularly adapted to be used in recording sounds to be later reproduced in synchronism with motion pictures. In this type of light valve a narrow slit having a width in the order of about one-half mil is 10 provided through which a beam of light is projected onto the sensitized surface of a uniformly moving ?lm. A vibratory current carrying conductor is placed in an angular position 2——2 of Fig. 1. 5 Fig. 3 is a longitudinal section taken along the line 3-3 of Fig. 2. Fig. 4 is an enlarged fragmentary view of the light slit and its associated vibrating conductor. Fig. 5 shows the length of ?lm having a varia- 10 ble area sound track thereon, as produced by the light valve. Fig. 6 is a schematic view showing the applica 5 over the slit so as to allow about one-half of the 15 length of the slit to be exposed to the beam of light when no current is ?owing through the conductor. A strong magnetic ?eld having its ?ux at right angles to the plane of the conductor is provided by a magnetic frame having its poles 20 placed closely adjacent the slit and conductor. When an alternating speech current is passed through the conductor the interaction between the magnetic ?eld and the magnetic force produced by the current ?owing through the con25 ductor causes the conductor to vibrate back and forth in accordance with the amplitude and frequency of the current thus changing the length of the exposed portion of the slit to the beam of light. 30 In my ore-pending application Serial No. 28,109, ?led June 24, 1935, for Sound recording, I have disclosed and claimed a light valve having a single electrical conductor vibratile at the frequencies to be recorded which is placed 35 across an aperture for producing a noiseless sound track of the double hump type. While it contains claims generic to the arrangement disclosed in detail here, that case speci?cally dis~ closes the use of a triangular aperture in the 40 path of the recording light beam, the single conductor moving parallel to the base of the tri- angular aperture. An object of the present invention is to adapt the apparatus of my co-pending application rei.» ferred to above to the recording of a noiseless sound track of the single hump type. This is accomplished by modulating the recording light beam by means of a single conductor moving angularly with respect to a rectangular 50 slit, The invention further relates to improvements in the mounting for the single string conductor. This invention is illustrated in the accompanying drawings in which: 55 Fig. 1 is a transverse section of a light valve tion of a noise reduction circuit. Figs. 7 and 8 are diagrammatic views showing the method of adjusting the biasing of the vibratile conductor. Fig. 9 is an enlarged fragmentary view of a positive ?lm having a variable area sound track resulting from the use of the noise reduction circuit shown in Fig. 6. Fig. l0 is an enlarged fragmentary view Show ing a sound track produced by the noise reduc~ tion circuit in Fig. 6. Referring now to Fig. 1, an exciter lamp I of constant intensity projects a beam of light 2 through a pair of condenser lenses 3. from whence it is focused to a point F within the light valve generally indicated at 4. Here the beam of light 2 is changed into a narrow slit of light of varying length. An objective lens 5 focuses the slit of light upon the sensitized surface of a continuously moving ?lm 6. Referring now to Figs. 1, 2, and 3, the light 15 20 25 30 valve 4 comprises a magnetic frame made up of 35 a base plate ‘I of magnetic material, which is se~ cured at its outer ends to the depending legs 3 and 9 of an upper magnetic frame Ill by means of screws II. The upper frame I 0 has a hollow core I2 provided thereon, which acts as one pole 40 of the magnet. A magnetic coil l3 receives a substantially constant direct current to produce a magnetic ?ux between the core l2 and a pole piece !4, which is secured to the lower base plate ‘l in alignment with the core l2, as shown in Fig. 45 1. The pole piece i6 is provided with an a er~ ture l5 to allow the beam of light to be pro jected therethro-ugh. The ends of the core If! and the pole piece M are placed closely adjacent each other so as to produce as strong a magnetic 50 flux as P08811318 Mounted on the base plate 1 adjacent the pole piece M are a pair of bridges I6 and H, having raised portions 18 and I9, upon which a vibrating conductor 20 rests. The bridges l6 and I‘! are 55 2 2,131,293 formed of insulating material such as Bakelite or hard rubber. The conductor 20 is secured. at one end to a Windlass 2|, for the purpose of adjusting the tension of the conductor 20. The other end of conductor 20 is passed around a spring pressed arm 23 and is secured to a Windlass 25 similar to that of 2!. The arm 23 is pivotable about a stud 24 and is urged outwardly toward the leg 8 by a torsion spring ti thus serving to prevent undue 10 tension from being placed upon the conductor 20. The windlasses 2i and 25 are electrically con nected by means of conductors 46 and 41 to ter minals 22 and 35 which, in turn, are connected through wires 56 and 5'! to suitable sound record 15 ing ampli?ers not shown. When a current is passed through the coductor 20, the interaction between the magnetic ?eld set up by the con ductor 2i] and the magnetic ?eld between the hollow core l2 and the pole pieces l4 and I5 will 20 cause a movement of the conductor 20 to one side or the other depending on the direction of the current. Referring now to Fig. 1, the beam of light 2 is focused upon a slit 34 de?ned by a pair of 25 slit forming members 26 and 2'! which are se cured upon supporting members 28 and 29 by means of clamping plates 39 and 3!. The sides of the members and 2'! are engaged by a pair of transversely extending plates (l8 and 49, also 30 secured by means of the clamping plates 3% and Si to de?ne the ends of the slit 3G. Of course, it should be understood that the slit 34 may and the slit 34 and also the initial position of the conductor 20 at no modulation may be varied. At Fig. 5 is shown a section of a positive print of a moving picture ?lm 44, having a variable area sound track portion 45 at one edge thereof formed by the passage of the ?lm before the light valve 4, Referring to Figs. 6, 7, and 8, I will now de scribe the application of noise reduction to the recording of sound by my improved light valve. 10 The recording circuit (Fig. 6) comprises a micro phone EG wherein sound waves are received and are translated into electrical currents of equiva lent wave form and proportionate amplitude. In circuit with the microphone 5B is an ampli?er 5| and a transformer 52 which supplies an ampli ?ed audio frequency current to the vibrating conductor 26 of the light valve 4. A noise re duction ampli?er 53 and recti?er 54 are shunted across the light valve circuit to provide a bias 20 neutralizing current through the conductor 20. Biasing current is provided by a battery 6i so as to hold the conductor 29 in the position shown by the dot and dash lines 29 of Fig. 4 when. no or little sound is being recorded. Thus the center of modulation as represented by the line 58 (Fig. 9) is held to the left of the center of the sound track 59 when recording low level sounds as at point L. When high level sounds are recorded, a current which increases in proportion to the 30 increase in level of the sound is impressed upon the ampli?er 53 and recti?er 54. The recti?ed also de?ned by the edges of the pole piece 14. current is fed to the conductor iii in a direction The members 22 and 29 are secured to the base 35 plate I by means of screws such as 32 and 33. Referring now to Fig. 4, the vibrating con opposite to that fed by the battery iii to thus neutralize the biasing current produced by the battery 6i. This neutralizing of the biasing cur ductor 29 is so adjusted with respect to the slit 34 formed by the members 26 and 2'! that it crosses it at a slight angle, which in the present 40 instance is slightly over one degree. Due to the fact that the natural period of vibration should preferably be above the range of audibility, it is necessary to keep the mass of the conductor 20 as small as possible. In this instance the con ductor 263 is in the form of a ?at ribbon about .0005" thick and about .006" wide and is con structed of Duralumin or other light material. These dimensions of course may be varied in accordance with different conditions and re quirements. When no current is ?owing, the conductor 29 covers approximately one—half of the area of the slit 34. When an alternating cur rent causes the center of modulation of the con ductor 2E1 to take a position shown by the full lines of Fig. 4. Thus the center of modulations for high level sounds as shown at point H (Fig. 9) is shifted toward the center of the sound track 59. The amount of biasing of the conductor is gen erally dependent upon the kind of sound being recorded. When recording dialogue or music in . which the volume is low, or where the change in volume is gradual, the main biasing position of the conductor may be brought nearer to its clos ing position than in the case of recording stac cato sounds such as are produced by a piano or harp. In recording the latter type of sound, rent is passed through the terminals 22 and 35, more leeway has to be given to the conductor to prevent the high level wave forms from being the conductor 26 is caused to move in a direction clipped. 55 perpendicular to the magnetic flux between the hollow core l2 and the pole piece M so as to change the length of the exposed portion of the slit M. The tension and angle of the conductor 2E5 is so adjusted that at full modulation the 60 entire slit 34 is covered at one instant while at another instant the whole area of the slit is ex posed. This exposure of the slit 34 is, of course, directly proportional to the amplitude of the current passing through the conductor. In order to provide adjustment of the conductor (i5 This change in biasing position of the conductor is accomplished by means of variable resistance 63 (Fig. 6) and may be effected during recording whenever the tempo of the sound is changed. The change may be made between dif ferent types of recordings when the recorder is stopped or during operation of the recorder when 60 the operator is aware of the nature of the sound to be recorded before impression thereof. The amount of biasing is generally determined by the amount of margin betwen a depression of a wave form and the edge of the sound track as justably secured to the bridges l6 and I‘! by indicated at M (Fig. 8). Referring to Figs. 7 and 8, the margin may also be determined by the dis— tance from the left hand edge 65 of the light slit 34 to the position of the conductor 20 at the upper limit of its excursions as indicated by the 70 dotted line 55. In setting the biasing position of the conductor 2%, the variable resistance 63 is manipulated until the distance X, representing means of adjusting screws 42 and 43. one-half of the amplitude of the conductor excur 26 in relation to the slit 3d, the bridges l5 and l? have adjusting jaws 36, 37, 3S and 39 thereon. These jaws are preferably formed of a spring ma terial and are secured at their rear ends to the 70 bridges l6 and I’! by screws 40 and M. The forward ends of the jaws are bent inward to en gage the sides of the conductor 20 and are ad Thus, 75 both the angle made between the conductor 20 sions at an arbitrary low level single frequency 75 2,131,293 sound, is allowed to reach a certain percentage .of the distance D (between the zero line of modu~ lation in the biasing position and the edge of the sound track) ; this percentage, of course, depend ing on the type of sound being recorded. In recording soft sounds, the distance X may be allowed to cover as much as 85% of the distance D. In the example shown in Fig. 8, the variable 10 resistance 63 is set so that X will equal one-half D when the conductor is in its biased position. Thus, the margin for low level sounds is indicated by the dimension M. When the amplitude of the sounds is increased to a point at which X exceeds one-half D the change in biasing current causes the mean position of the conductor 20 to be moved downward so as to maintain approximately the same average ratio of X to D. This ratio will re main approximately constant until the conductor 20 20 reaches its unbiased position as shown by the dotted lines 20'. In this position the ratio of M1 to D1 is still approximately equal to the ratio of M to D. As higher amplitudes are recorded, the zero line of modulation remains at C, provi 25 sion being made in the recti?er R to prevent a shift of the zero line to the right of C, while the margin again becomes smaller as at Mh to ac commodate the higher amplitudes. Referring to Fig. 9, the zero line of modula 30 tion is indicated by the center line 58. Where no sound is recorded on the ?lm only a narrow path of transparency 61 traverses the sound track. As modulations are recorded and increased, the zero line of modulation is moved outwardly toward 35 the center of the sound track until the conductor reaches its unbiased position as indicated by the point H. 40 45 50 55 Due to the fact that the edges of the sound track are formed by the acute angle between the conductor 20 and the light slit 34, these edges will not form sharp lines but will gradually pass from clear transparency to opacity as shown in Fig. 10. The amount of distortion, however, pro duced by this shaded zone 68 is negligible due to the fact that its dimension as measured trans versely of the direction of the ?lm travel remains constant and thus it is unable in itself to mate rially effect a varying change of light passing therethrough; it being understood, of course, that the reproduction of sound is dependent upon a change in the amount of light passing through the slit above the lowest audible frequency. The only possible effect of the shaded zone caused by frequency variations in the sound being recorded is to vary the direct current component, which does not change the frequencies making up the sound wave. 3 The biasing of the conductor 20 may also be ac complished by applying the recti?ed current from the recti?er 54, which varies in accordance with the amplitude of the sounds being recorded, in a positive sense to the conductor 20. In this case, the normal position of the conductor 20 would be mechanically adjusted so that at low level modu lation it would be to the left of the center of the sound track or in a position shown by the full lines 20 of the conductor Fig. 7. With the in 10 crease in amplitude of the sound being recorded, the corresponding increase in recti?ed current from the recti?er 54 would shift the center of modulation of the conductor 20 to the position shown by the dotted lines 20'. That is, instead of 15 variably neutralizing a ?xed electrical bias, the ?xed electrical bias is eliminated and the recti?ed current variably biases the conductor in accord ance with the average amplitude of the sound waves being recorded. 20 Having thus described the invention what is claimed as new and desired to secure by Letters Patent is: 1. A device for recording sound waves which comprises a system for transmitting light from a source to a photographic ?lm, means for varying the amount of transmitted light comprising a member arranged in a magnetic ?eld and having an elongated slit therein, a single electrical con ductor arranged in the same magnetic ?eld as 30 said member and adjacent the slit in said member to de?ne a light transmitting slot, means for sup plying electrical current to said conductor to e?’ect variation in the space relation between said conductor and said slit in accordance with the in 85 stantaneous values of said currents, and means for supplying a current to said conductor to effect a variation in the spaced relation of said conductor with respect to said slit in accordance with the envelope of said electrical currents, said conductor and said slit being disposed in oblique relation to each other. 2. In combination, a member located in a mag netic ?eld and having a ?xed elongated aperture therein, the same movable element suspended in 45 a magnetic ?eld and disposed in oblique relation to the aperture in said member, means to supply modulated electrical currents to said movable ele ment to effect movement thereof in front of said aperture in said member in accordance with the 50 instantaneous values of said currents, and means to supply current to said movable element to effect movement thereof in front of said aperture in said member in accordance with the envelope of said electrical currents. 55 BURTON F. MILLER. CERTIFICATE OF CORRECTION. Patent No. 2,151,295. September 27, 1958. BURTON F. MILLER. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, second column, line k5, claim 2, for the words "the same" read a; line k6, same claim, for "a" read the same; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. Signed and sealed this 21st day of March, ‘A. D. 1959. Henry Van Arsdale. (Seal) Acting Commissioner of Patents. CERTIFICATE OF CORRECTION. Patent No. 2,151,295.‘ ' - - September 27.1958. BURTON F. MILLER. It is hereby certified that error appears in the printed specification ' of the above numbered patent requiring correction as follows: Page 5 , second column, line 1L5, claim 2, for the words "the same" road a; line liéysame claim, for "a" read the same; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. Signed and sealed this 21st day of March, ‘A. D. 1939. Henry Van Arsdale. (Seal) Acting Comissioner of Patents.