Ampex Corporation

Other

Ampex Systems Corporation

Lasertape Systems, Inc.

David R Rodal

Nathan W Osborn

Lawrence Matthias Bryant

Marshall Williams

Robert B Steele

Harold V Clark

Glenn T Yoshida

James W Dickson

An electronic circuit is described which will allow an acoustoptic deflector to be used in multi-frequency mode at high power levels with a minimum amount of intermodulation between each frequency. Reduction of interference between multiple separate signal frequencies is achieved by precise control of the individual phasing of each separate frequency relative to a common reference frequency. The relative phase of each frequency is also controlled so that a low maximum power is achieved for the combined signal that is presented to the acousto-optic deflector without decreasing the overall average power of the multiple signal frequencies. The present invention is useful in systems such as optical data storage on tape or disk, optical printing and imaging, and acousto-optic signal or information processing.

Frequency, phase and amplitude control apparatus and method for

A feedforward circuit applies a capstan drive current, or its equivalent, to the reel tension servo circuits whose associated reels are transporting the tape. The additional drive current to the reel drive motors increases the rotational velocity of the reels to maintain the same resultant acceleration between the tape driven by the capstan and the tape being transported between reels. Since the tape pack affects the gain of the feedforward circuit, a preselected average gain corresponding to the mean tape pack diameter is used to match different cassette sizes. A microprocessor may be used to provide the various signals and may vary the gain of the feedforward circuit not only in response to reel size but also in response to instantaneous reel tape pack diameter.

Tape transport control system with a feedforward capstan drive to the

An end-of-tape detection apparatus provides a constant accumulated total of the revolutions of the supply and takeup reels relative to the true end-of-tape defined by the leader-to-tape splice. Counter means stores a value indicative of the true end-of-tape, and also counts and stores the accumulated total of revolutions as the tape is wound onto a reel. Thereafter as tape is pulled from the reel, the approaching end-of-tape is accurately known in terms of the remaining revolutions of the reel. A microprocessor uses the stored value to determine the point at which deceleration of the tape should begin, whereby the tape rapidly is decelerated to a selected speed just prior to true end-of-tape. The tape is stopped upon sensing the leader-to-tape splice.

Circuit for detecting the end of a tape by counting reel revolutions

Tape guides of a magnetic tape transport machine are controlled during movement by sensing the position of the member as it moves along a defined path in varying velocity corresponding to the position. The member is initially accelerated at a selected rate to a maximum velocity which is then maintained until a distance close to the end position is reached. Velocity is then reduced at a selected rate until another position closer to the end position is reached. At this position a final velocity is maintained until the end is reached. A determination is made of how closely the second distance from the end coincided with reaching the final velocity. The length of the first distance from the end position is adjusted to reduce the difference between the coincidence of reaching the second distance and the final velocity. Further, the sensed final position of the member is retained as the target final position for the subsequent operation.

Method and apparatus for controlling deployment of a tape transport

In a tape drive system, a dynamic brake control circuit provides dynamic braking for slowing and stopping an associated tape reel and motor system in the event of a power failure. Upon sensing a power failure, the electrical energy stored in a capacitor supplies electrical energy to enable the control circuit, which in turn supplies a controlled conductive path for the flow of a dynamic braking current due to the back electromotive force signal generated by the motor, to effect the controlled dynamic braking of the drive motor to a stop.

Dynamic brake control for a tape drive system

A method and apparatus for controlling the capstan servo of a magnetic video tape recording and reproducing machine is disclosed. The invention provides almost instantaneous color framing and synchronous control track lock when accelerating from a very slow tape velocity up to normal velocity. An embodiment of the apparatus also stops the tape at a predetermined position relative to control track transitions when stopping the machine from a noncontrol track lock operating mode, such as shuttle, variable velocity reproducing and jog.

Rotary head tape transport servo system having high speed servo lock

A digitally controlled motor drive system using a pulse width modulated motor drive receives a desired motor velocity signal and an actual motor velocity signal and it provides a corresponding velocity error signal. The velocity error signal is adjusted in response to a change in the value of a power voltage supplied to the motor. The velocity error signal may be compensated for back electromotive force and/or for static friction in the motor, if desired. The system is simple, reliable and cost effective.

Adaptive digitally controlled motor drive system and method

In a tape transport apparatus, a first servo feedback loop is provided for correcting tape tension by adjusting the rotation of a tape reel in response to the sensed position of a tension arm that engages the moving tape. A second feedback loop senses the rate of change in the position of the tension arm and responsively damps the tension arm position changes by means of a lead circuit which causes a torque motor coupled to said pivotable arm to move in opposition to the tension arm position changes.

Reel servo control with resonance damping circuit

An optical sensing circuit useful for detecting the end of a moving tape in a tape transport includes a light source and a light sensor which are closely spaced across a gap. The radiation output of the light source is modulated at a selected frequency which is determined by the operating frequency of a frequency detector. In the absence of a light obstruction, such as passage of the tape in the optical path between the light source and the light sensor, the modulated output from the light source is detected by the sensor. The processed signal from the sensor, which is characterized by the modulation frequency, is applied to the frequency detector. The detector recognizes only those signals having the modulated frequency, and does not respond to signals of different frequencies, which may result from impingement of other radiation than that from the light source on the photosensor.

Ambient light insensitive circuit with frequency matching

A capstan servo for moving video tape with variable speed during playback controls the tape speed according to time period inputs. The input specifies the number of seconds per hour of program length, for example, that a segment of recorded video information is to be expanded or compressed compared relative to its normal real time playback length. The speed of tape transport during playback is varied by locking the reproduced control track vertical sync signal to a synthesized time adjustable reference signal.

Video tape transport servo for variable tape speed control

A synthetic control track signal is provided for a magnetic video tape recording and/or reproducing machine having a motor driven capstan and capstan servo which controls the speed of the tape during recording and reproducing. The synthetic signal enables the capstan servo to operate when the control track signal has not been recorded or has been improperly recorded. The synthetic signal is generated from vertical synchronization information extracted from the video information extracted signal.

Synthetic control track signal producing apparatus for video tape

A power fail circuit provides protection for tape such as used in the tape transport apparatus of a video recorder in the event of a failure of the external power supply. The tape transport apparatus includes as a feature the provision of an electrical error signal used to govern drive motors to maintain substantially constant tape tension when the system is operating normally. After power failure occurs, the power fail circuit continues to respond to the error signal by coupling current from the drive motors to provide dynamic braking. Further, current taken from the drive motors selectively is coupled to an energy storage device operatively associated with the system power supply, to provide augmenting energy from the kinetic energy of the motors for continued control of the power fail circuit as the drive motors are caused to decelerate under control to stop.

Power fail servo system

An improved drive circuitry for controlling the deflection of a bimorph comprising a pair of electrically poled piezo-ceramic elements bonded to a common substrate is disclosed which applies deflection voltage in a manner whereby the polarity is always in the poling direction of each of the elements so that depolarization of the piezo-ceramic elements does not occur. The circuitry applies a common polarity D. C. biasing voltage to both of the piezo-ceramic elements of the bimorph and also applies oppositely phased A. C. deflection signals to the respective piezo-ceramic elements.

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Palo Alto, CA, United States of America

David R Rodal