US3484530A - Musical instrument employing film sound track on cathode ray tube screen - Google Patents

Description

Dec. 16. 21969 R. E. RUPERT MUSICAL INSTRUMENT EMPLOYING FILM SOUND TRACK ON CATHODE RAY TUBE SCREEN Filed April 26, 1966 2 Sheets-Sheet 1 PRE AMPLIFIER CIRCUIT LOW FREQUENCY MODULATION DETECTOR VOLUME LEVEL SENSING CIRCUIT VERT|CAL VERTICAL DRIVER CIRCUIT CONVERTQR HORIZONTAL EFLECTION C'RCUIT CIRCUIT DEFLECTION OSCILLATOR C|RCU|T HIGH VOLTAGE POWER SUPPLY CIRCUIT SWITCHING CIRCUIT HORIZONTAL DEFLECTION CIRCUIT VERT ICAL AMPLIFIER CIRCUIT LOUD SPEAKER DEFLECTION CIRCUIT VERTICAL 'OSCILLATOR CIRCUIT F IG. 2

CATHODE TUBE AMPLIFIER LOUD CIRCUIT SPEAKER INVENTOR ROBERT E. RUPERT wmflmk 092;:

ATTORNEY R. E. RUPERT 3,484,530 MUSICAL INSTRUMENT EMPLOYING FILM SOUND TRACK Dec. 16. 1969 ON CATHODE RAY TUBE SCREEN 2 Sheets- Sheet 2 Filed April 26, 1966 .EDOEO .EDOwtU mmvawmw D304 .IDOEG mwwwrmk .EDOEO mokikzmmmmhrn ZOFQMTEMO .EDOmzO FBOEQ 0262mm MEDJO United States Patent 3,484,530 MUSICAL INSTRUMENT EMPLOYING FILM SOUND TRACK ()N CATHODE RAY TUBE SCREEN Robert E. Rupert, 60 Whittier Road, Wakefield, Mass. 01880 Filed Apr. 26, 1966, Ser. No. 545,463 Int. Cl. Gh 3/06, 3/04 U.S. Cl. 84-1.18 8 Claims ABSTRACT OF THE DISCLOSURE This invention relates to electro-optic apparatus for producing musical tones accurately simulating the tones of a selected musical instrument such as a conventional brass, woodwind or stringed instrument. According to the invention, a cathode ray tube with a short persistency screen phosphor is used in conjunction with a film sound track to provide a varying electric current to be fed into a loud speaker for the production of tones characteristic of the selected musical instrument.

Various means may be employed to energize the cathode ray tube, three such means being illustrated in the drawings, of which:

FIG. 1 is a diagrammatic layout of apparatus for producing musical tones in response to a vocal input;

FIG. 2 is a diagrammatic layout of apparatus constituting a musical instrument to be played by striking keys like those of a piano;

FIG. 3 is a diagrammatic layout of a modification of the invention, and,

FIG. 4 is a view in front elevation of a series of variable area optically recorded sound tracks applied to the face of a cathode ray tube.

In FIG. 1 are illustrated several conventional electronic circuits coupled to a relatively simple electro-optic assembly that reproduces optically recorded musical instrument notes. The reproduced notes are stimulated by vocal sounds fed to the audio input circuits by a contact type microphone.

Because a full range of notes on the musical scale can be reproduced in step with the vocal signals applied, this device constitutes a playable musical instrument like any conventional brass, woodwind or string instrument, but is far simpler to play since only the vocal cords and related muscles are involved.

True reproduction of instrumental tones is further enhanced by detecting the low frequency modulation and changing volume of each note as they are fed to the circuits and applying these effects to the delivered recorded musical note. The function of each of the circuits is as follows:

A microphone 12 receiving vocal sound waves from the player passes a signal current to the audio pre-amphfier circuit 13. The audio pro-amplifier circuit 13 amplifies the microphone signal currents and passes them to the driver circuit 14 where suflicient power build-up of the signal occurs to operate the frequency-to-DC. convertor circuit 15. The frequency-to-DC. convertor circuit will produce an output voltage that is proportional to the fundamental frequency applied. Since the fundamental in most complex waveforms has the highest amplitude of 3,484,530 Patented Dec. 16, 1969 all its components, part of the frequency-to-D.C. convertor circuit is able to hold the signal level constant, similar to an automatic volume control circuit, so that the peaks will be available for detection and counting. The frequency-to-DC. conversion voltage is then applied to a horizontal deflection circuit 16 to drive an electron beam 3 horizontally in the electrostatic cathode ray tube 1. Each note on the chromatic scale can be represented by a horizontal position on the phosphor screen face of the cathode ray tube. At each horizontal position on the face of the cathode ray tube 1 is attached a section of photographic film sound track 4 similar to that used in motion picture projection, the sound track being a recording of notes from the selected musical instrument. The electron beam 3 thus will produce a spot 18 of light behind each film section. A scanning motion of the beam is caused by having the beam 3 deflected vertically by appropriate voltages on the cathode ray tube vertical deflection plates. These voltages are generated in the vertical oscillator circuit 10 and the vertical deflection circuit 11. The vertical oscillator frequency is set so that the scanning rate of the light spot on the cathode ray tube will produce a signal into the optical system that gives the proper musical pitch, the light beam having been modulated by the film sound track in its path. The vertical deflection voltage generated in the vertical deflection circuit 11 and whose frequency is controlled by the vertical oscillator 16, has a sawtooth or ramp wave form which results in the beam moving uniformly in the vertical direction at a rate depending on the slope of the ramp, and returning rapidly to its starting point when the trailing edge of the wave passes. The trailing edge of the waveform produces the return trace; this may be eliminated by insertion of a blanking circuit. The circuits described here are commonly found in todays modern television receivers. Modulated light rays 5 emanating from the film sound track are collected by the light collector 6 which may be a concave mirror, and are reflected and focused on the light sensor 8. This transducer responds to the visible light energy emitted by the screen phosphor 2 and generates signal currents which are amplified in circuit 9 and then passed on to the loud speaker system 19. Low frequency modulation of the generated musical tone is accomplished by separating this frequency from the input signal in circuit 17, the low frequency modulation detector, and applying the resulting signal to the cathode of the cathode ray tube and the electron beam in turn. Loudness or volume of the signal current is detected in a volume level sensing circuit 21 and also is superimposed on the cathode potential of the cathode ray tube circuit where it influences the beam intensity and the resulting light spot behind the film sound track. Each electronic circuit in FIG. 1 is assumed to have its power supplied. A high voltage power supply circuit 18 has been added separately for the cathode ray tube. Thus by the use of such apparatus a vocal melody is transformed into an instrumental melody.

In the apparatus diagrammatically illustrated in FIG. 2, a film sound track 4 is employed in conjunction with a cathode ray tube 1, a sensor 8 and a loud speaker 19. The parts of the apparatus employed to energize the tube, however, are arranged to be played like a piano with a set of keys, one such key 22 being illustrated by way of example. When the key is depressed, the switching circuit 24 is activated and causes a potential to change in the cathode ray tube which turns on the electron beam. The electron beam 3 excites the phosphor screen 2 on the face of the cathode ray tube and emits visible light energy. The light energy so emitted is caused to pass through a. section of photographic film sound track 4 that has been attached to the front of the cathode ray tube. The optically recorded sound information contained on the film sound track modulates the light passing through it as light of varying intensity. The switching circuit 24 also energizes the horizontal deflection circuit 16 causing a predetermined amount of deflection voltage to appear on the horizontal deflection plates within the tube which positions the spot on an appropriate film sound track section. Scanning of the section of film sound track is accomplished by moving the beam vertically over the track by applying appropriate voltages to the vertical deflection plates of the cathode ray tube. These voltages are generated in the vertical deflection circuit 11 and frequency controlled by the oscillations produced in the vertical oscillator circuit 10. The vertical deflection voltage applied to the vertical deflection plates of the cathode ray tube has a sawtooth or ramp waveform which results in the beam moving uniformly in the vertical direction at a rate depending on the slope of the ramp and returning rapidly to its starting point when the trailing edge of the wave passes. The trailing edge of the waveform produces the return trace; this may be eliminated by insertion of a blanking circuit. The circuits described here are commonly found in todays modern television receivers.

The emerging light rays 5 are then gathered by the light energy collector 6. The light collector collects, reflects and focuses the light rays on the light sensor 8. The focused rays 7 are shown. Light rays falling on the light sensor induce electrical signal currents in the light sensor circuit due to the modulating action of the photographic film sound strip which is interposed between the phosphor screen and the optical system. These currents are then further amplified in the amplifier circuit 9 coupled to the photocell 8. The amplified musical tones are then heard over the loudspeaker system 19 attached to the amplifier circuit 9.

To produce the several notes of a scale, a corresponding number of parallel sound tracks are provided on the film 4, these tracks being photo recordings of notes of different pitch as played on the selected instrument. There is also a corresponding number of keys 22, each key being connected to the tube 1 through its own horizontal deflector circuit 16 by which the voltage transmitted to the tube is adjusted to direct and hold the electron beam 3 to the particular sound track on the film 4 which corresponds to the key 22 which is being depressed.

In the systems described and illustrated in FIGS. 1 and 2, one section of film sound track 4 is employed for each musical note that is to be generated. Thus a number of different tracks are required to reproduce a number of different musical notes. Three such different tracks 4a, 4b and 4c are shown in FIG. 4. This arrangement requires means for deflecting the electron beam to various predetermined horizontal positions in order to scan each film strip representing a note. An alternate means of generating notes of different pitch by the use of only one strip of film sound track is illustrated in the modification of FIG. 3.

In this embodiment a microphone 12 receiving vocal sound waves from the operator passes the signal current to the audio preamplifier circuit 13. The audio pre-amplifier circuit 13 amplifies the microphone signal currents and passes them to thbe driver circuit 14 where the signal overdrives an amplifying tube or transistor to produce a nearly square wave form in the output. The square wave is then fed to a differentiator circuit 26 where the leading and trailing edges of the square wave signal produce spikes or pulses of short duration. These pulses are then fed to a trigger circuit 28 that responds only to either the leading or the trailing edge pulses (positive going pulses or negative going pulses, respectively). There will be one pulse of this sort for each electrical cycle of the fundamental in the vocal input signal. These pulses are now used to initiate and synchronously control the frequency of oscillation in a multivibrator circuit 30. The square wave voltages produced here are then fed to a vertical deflection circuit 32 which has built into it a ramp generator that will produce a sawtootlrvoltage wave form of constant peak amplitude. While these waveforms are of constant amplitude they are characterized by ramps that vary in slope angle, or rate of buildup, the rate being determined and controlled by the multivibrator frequency by means of an integration network in the ramp generator. These sawtooth waveforms, whose ramp angles vary with frequency in step with the vocal input, are then used to deflect the electron beam vertically by means of the vertical deflection circuit and to thereby cause the spot 18 to scan the film strip at varying rates and thus produce diflerent pitched notes. The film sound track in this case contains several complete optically recorded cycles of the lowest pitched musical note, the exact numher being determined by the number of oscillations required during integration to produce the peak ramp voltage. Since this arrangement requires only one film sound track to reproduce the sound of one musical instrument, additional space is available on the tube face for other sound track strips as suggested in FIG. 4 permitting several musical instruments to be reproduced in the same system, each sound track being formed to reproduce the overtones of the instrument it represents. The player then selects the instrument sound he wishes to reproduce by an instrument selector circuit 34 which supplies a predetermined amount of deflection voltage to the horizontal deflection plates of the cathode ray tube for each selector position. This deflection voltage is fed through the horizontal deflection circuit 16 to the direct and hold the electron beam onto the proper film strip with the vertical scanning motion being applied as previously described. Low frequency modulation and volume techniques are utilized as described and illustrated in FIG. 1.

While the invention has been described with particular reference to the illustrted embodiments, it will be understood that numerous modifications thereto will appear to those skilled in the art. For example, the sounds of two or more instruments may be reproduced simultaneously by the use of a cathode ray tube with a double (or more) beam and associated deflecting plates and circuitry. In such a case the two (or more) beams may be scanned over separate sound tracks, each of a different instrument and thereby reproduce the two sounds from a single input. As another modification, the concave mirror may be replaced by a lens interposed between the tube and the transducer 8. Various transducing devices may be employed such as silicon detectors, photo multiplying tubes and the like. Obviously, the sound tracks may be arranged in a variety of positions on the tube face such as horizontally or vertically, side by side or sections end to end with appropriate modification of the control circuitry. The track itself may be of the variable area or of the variable density type, as desired.

Accordingly, the above description and accompanying drawings should be taken as illustrative of the invention and not in a limiting sense.

Having thus described the invention, what I claim and desire to obtain by Letters Patent of the United States is:

1. Apparatus for producing musical tones accurately simulating tones of a selected musical instrument, comprising a cathode ray tube having a phosphor screen, a film sound track on which are optically recorded in individual areas, individual tones from said instrument, means for energizing said tube to project an electron beam from the cathode to the screen and to scan a portion of the screen, a light sensor, a light collector arranged to focus on said sensor the light rays emitted by said screen past said film, a loud speaker, means for amplifying the variable current from the sensor to the loud speaker, and means of controlling said energizing means to limit the scanning movements of said electron beam to predetermined ones of said individual areas.

2. Apparatus as described in claim 1, said film having a series of parallel sound tracks thereon for selective scanning by said electron beam, said tracks corresponding respectively to a series of notes in a musical scale.

3. Apparatus as described in claim 2, said controlling means including means operable to select the successive musical notes to be sounded by said loud speaker.

4. Apparatus as described in claim 3, said controlling means including a horizontal deflector circuit for each of said parallel sound tracks and a switch key for each set of horizontal and vertical deflector circuits.

5. Apparatus as described in claim 2, said controlling means including a microphone into which notes of dif-.,

ferent pitch may be successively sounded, a horizontal deflection circuit connected between said microphone and said cathode ray tube, a vertical deflection circuit operatively connected to said tube, and electrical means connected between said microphone and tube and responsive to the fundamental pitch of a note sounded into said microphone to limit the horizontal scanning movements of said electron beam to the sound track corresponding to said pitch.

6. Apparatus for producing musical tones simulating tones of at least one musical instrument, comprising (a) a cathode ray tube, (b) a film sound track disposed in front of the tube face, (0) said track having optically recorded thereon tones from said instrument, (d) means for energizing said tube to project at least one electron beam onto said tube face to illuminate a spot thereon in register with said track, (e) a transducer adapted to convert light signals into electrical signals, (f) means for directing light signals from said tube passing through said track onto said transducer, (g) a loudspeaker, (h) means for amplifying the electrical signals from said transducer to drive said loudspeaker, and, (i) means responsive to a tone signal input for scanning said spot aong said track at a rate varying with the input frequency to thereby produce different pitched notes at said loudspeaker.

7. Apparatus according to claim 6 including a plurality of tracks disposed in front of the tube face, each of said tracks having optically recorded thereon tones from different instruments and means connected to said tube for directing said beam into register with a selected one of said tracks.

8. Apparatus for producing musical tones simulating tones of at least one musical instrument, comprising (a) a film sound track having optically recorded thereon tones from said instrument,

(b) means for illuminating a spot in register with said track,

(c) a transducer adapted to convert light signals into electrical signals,

((1) means for directions light signals passing through said track onto said transducer,

(e) a loudspeaker,

(f) means for amplifying the electrical signals from said transducer to drive said loudspeaker, and,

(g) voice operated means responsive to a variable vocal input signal for the scanning of said spot along said track at a rate variable with said input signal and thereby produce tones at said loudspeaker characteristic of said instrument.

References Cited UNITED STATES PATENTS 2,221,097 12/ 1 940 Koehl 841.18 2,148,166 2/1939 Kucher 84l.18 2,528,020 10/ 1950 Sunstein 841.28

H. K. SAAL BACH, Primary Examiner F. P. BUTLER, Assistant Examiner US. Cl. X.R.

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