Telecine system control electronics to provide synchronism between the projector pulldown and television scan over a wide range of pulldown rates

Claim 2

In a telecine system comprising a film projector having a pulsed pull down and a television camera viewing the image projected by the projector, means to provide for synchronizing the frame projection rate of said projector with the scan of said television camera comprising: a. means to generate command signals of a variable rate from zero cycles per second to the television field rate, each signal indicating that the film in the projector is to be pulled down to index the next frame for projection; b. means having as an input the vertical sync command of said television camera to synchronize the vertical scan of the television camera and the projection of an image by the projector to the camera pickup tube so that the beginning and end of said projection occurs during substantially the same portion of each vertical scan; c. means to generate a pulse beginning a first predetermined time after the end of said projection and ending a second predetermined time before the beginning of the next projection; and d. means responsive to said command signals and said pulse to actuate the projector pulldown when one of each of said signals and said pulses is present at the same time.

Claim 3

The invention according to claim 1 wherein said synchronizing means comprise: a. a rotatable shutter having at least one open portion said shutter being interposed between the projector lamp and the film gate in said projector; b. means to rotate said shutter; c. means coupled to said rotating means to provide a pulse output during at least a portion of the time when the open portion of said shutter is between said lamp and said gate; d. a phase detector having as inputs said pulse output and the vertical sync command of said television camera and providing an output indicative of the phase difference between the pulses of said pulse output and said sync command; e. control means responsive to said phase detector output to control the speed of said rotating means to maintain a predetermined phase difference between said pulse output and said sync command thereby causing the projection of an image to be synchronized with the television vertical scan.

Claim 4

The invention according to claim 2 wherein said means to rotate comprises an electric motor and said phase detector comprises at least a flip flop having its set input coupled to said pulse output and its reset input coupled to said sync command and said predetermined phase difference is such that said flip flop will be on and off for equal time periods and said control means comprise: a. a neTwork having said phase detector output as a first input and an offset voltage as a second input said network providing averaging of said phase detector output and summing of said averaged output with said off-set voltage, said offset voltage being selected to provide a sum of zero for the average resulting when said flip flop is on and off for equal times; and b. rate servo means comprising said motor, amplification means and a tachometer coupled to said motor, said amplification means providing its output to drive said motor and having as inputs, at a summing junction, the output of said tachometer, a voltage proportional to a nominal shutter rotation speed and the output of said network whereby said network output will provide a correction to said servo means when said shutter is not synchronized with said vertical scan.

Claim 5

The invention according to claim 3 and further including means to provide a visual indication of loss of synchronism.

Claim 6

The invention according to claim 1 wherein said second predetermined time is at least equal to the time required to accomplish a complete pull down.

Claim 7

The invention according to claim 5 wherein said vertical scan and projection of an image are so synchronized that one projection take place for each field of the vertical scan.

Claim 8

The invention according to claim 6 wherein the beginning and end of said projection is controlled by a shutter device interposed between a projection lamp and film image.

Claim 9

The invention according to claim 7 wherein said beginning and end of projection are timed to occur substantially within the vertical retrace time of the TV camera.

Claim 10

The invention according to claim 7 wherein the video signal from the TV camera provides the input for a visual display device arranged for viewing by a student in a vehicle simulator.

Claim 11

The invention according to claim 9 wherein said variable rate is commensurate with outputs determined by control settings on said simulator.

Claim 12

The invention according to claim 7 wherein said command signal generating means comprise means to generate pulses at said variable rate, a flip flop having said pulses as a set input and providing said command signals at its output and means to provide a reset pulse to said flip flop after each pull down pulse.

Claim 13

The invention according to claim 11 wherein said pulses at said variable rate are provided by a voltage controlled oscillator having an analog voltage input proportional to said variable rate.

Claim 14

The invention according to claim 11 wherein said means to generate said pulse comprises a one shot multivibrator timing circuit having the vertical sync command of said television camera as an input and adapted to provide an output the beginning of which is slightly delayed from the end of projection, and of a length which is less than the time between projections and said responsive means comprise an And gate having the outputs of said timing circuit and said command signals as inputs and providing its output as a projector pull down command.

Claim 15

The invention according to claim 13 wherein said means to provide said reset pulse comprise one shot multivibrator timing means having an input from said And gate and providing said reset pulse as an output of a predetermined time after obtaining an input.