Automatic beam blanking circuit for an electronic video player

Claim 2

In an electronic video player having film transporting apparaTus for continuously moving film past a film gate with the player operated in a play mode of operation, a flying spot scanner producing a beam to generate a moving spot of light on a display screen thereof in a raster having a predetermined horizontal-to-vertical aspect ratio for scanning the moving film at the film gate, means for stopping movement of the film to operate the player in a still mode repeatedly scanning the stopped film at the film gate, and means for changing the aspect ratio of the scanner raster to cause scanning of a smaller raster with the player in said still mode of operation; a protection circuit including in combination: first switch means for operation to one or the other of first and second positions corresponding, respectively, to a play mode and a still mode of operation of said player; static latching switch means having a trigger input; means for completing a conductive path through said static latching switch means and said first switch means with said first switch means in its second position, said path being opened with said switch means in its first position, said static latching switch means being normally nonconductive and being rendered conductive by the application of a trigger pulse thereto; interval timer means having a timer output and responsive to operation of said first switch means from its first to its second position for providing a timer output pulse a predetermined time interval after such operation of said first switch means with said first switch means remaining in its second position; means coupling the timer output of said interval timer means with the trigger input of said static latching switch means for applying the timer output pulse to said static latching switch means as a trigger pulse to render said static latching switch means conductive; and means responsive to conduction of said static latching switch means to cut off the beam in said flying spot scanner.

Claim 3

The combination according to claim 1 wherein said interval timer means includes charge storage means having first and second terminals, with the first terminal connected with a point of reference potential and the second terminal connected through a charging path to a source of charging potential with said first switch means operated to its second position, and threshold responsive circuit means connected to the second terminal of said charge storage means for producing the timer output pulse in response to attainment of a predetermined charge by said charge storage means, operation of said first switch means to said first position connecting said point of reference potential with said second terminal of said charge storage means, thereby disabling said interval timer means.

Claim 4

The combination according to claim 2 wherein said static latching switch has first and second terminals through which the conductive path is completed and said first switch means includes first and second movable contacts, and at least first, second and third stationary contacts; means connecting the first movable contact to a source of charging potential; means connecting the second movable contact to the point of reference potential; first circuit means coupling said first stationary contact with the charging path for said charge storage means, operation of said first switch means to its second position causing said first movable contact to engage said first stationary contact; second circuit means coupling said second stationary contact to the second terminal of said static latching switch; with said first switch means operated to said second position causing said second movable contact to engage said second stationary contact to complete the conductive path between said static latching switch and the point of reference potential; and means coupling the second terminal of said charge storage device with said third stationary contact, with operation of said first switch means to its first position causing said second movable contact to engage said third Stationary contact to prevent charging of said storage device.

Claim 5

In an electronic video film player having film transporting apparatus for continuously moving film past a film gate with the player operated in a play mode of operation, a flying spot scanner producing a beam to generate a moving spot of light on a display screen thereof in a raster having a predetermined horizontal-to-vertical aspect ratio for scanning the moving film at the film gate, means for stopping movement of the film to operate the player in a still mode to repeatedly scan the stopped film at the film gate, and means for changing the aspect ratio of the raster to cause scanning of a smaller raster with the player in a still mode of operation; a protection circuit including in combination: first switch means including at least first and second movable contacts coupled for simultaneous movement between first and second positions corresponding, respectively, to a play mode and a still mode of operation of said player; a first stationary contact for engagement by said first movable contact in said second position thereof; second and third stationary contacts for engagement with said second movable contact in said second and first positions, respectively; a source of operating potential; static latching switch means connected between said source of operating potential and said second stationary contact and having a gating input responsive to the application of a gating pulse thereto for rendering said static latching switch conductive; relaxation oscillator means including a timing capacitor with first and second terminals connected between a point of reference potential and a first junction, respectively, said oscillator producing an output pulse with a predetermined charge being attained by said timing capacitor; means supplying the output pulse of said relaxation oscillator to the gating input of said static latching switch as a gating pulse therefor; charging path means connected between the second terminal of said timing capacitor and said first stationary contact; first circuit means connecting the second terminal of said timing capacitor with said third stationary contact; second circuit means for coupling said first movable contact with said source of operating potential; third circuit means coupling said second movable contact with the point of reference potential; and fourth circuit means responsive to conduction of the static latching switch for blanking the beam in the flying spot scanner.

Claim 6

In an electronic video film player having film transporting apparatus for continuously moving film past a film gate with the player operated in a play mode of operation, a flying spot scanner producing a beam to generate a moving spot of light on a display screen thereof in a raster having a predetermined horizontal-to-vertical aspect ratio for scanning the moving film at the film gate, means for stopping movement of the film to operate the player in a still mode to repeatedly scan the stopped film at the film gate, and means for changing the aspect ratio of the raster to cause scanning of a smaller raster with the player in a still mode of operation; a protection circuit including in combination: first switch means including at least first and second movable contacts coupled for simultaneous movement between first and second positions corresponding, respectively, to a play mode and a still mode of operation of said player; a first stationary contact for engagement by said first movable contact in said second position thereof; second and third stationary contacts for engagement with said second movable contact in said second and first positions, respectively; a source of operating potential; static latching switch means connected between said source of operating potential and said second stationary contact and having a gating input responsive to the application of a gating pulse thereto for rendering said static latching switch conductive; relaxation oscillator means including a timing capacitor with first and second terminals connected between a point of reference potential and a first junction, respectively, said oscillator producing an output pulse with a predetermined charge being attained by said timing capacitor; means supplying the output pulse of said relaxation oscillator to the gating input of said static latching switch as a gating pulse therefor; charging path means connected between the second terminal of said timing capacitor and said first stationary contact; first circuit means connecting the second terminal of said timing capacitor with said third stationary contact; second circuit means for coupling said first movable contact with said source of operating potential; third circuit means coupling said second movable contact with the point of reference potential; and fourth circuit means responsive to conduction of the static latching switch for blanking the beam in the flying spot scanner.

Claim 7

The combination according to claim 4 wherein said static latching switch comprises a silicon controlled rectifier having an anode, cathode and gate, the anode of which is coupled with said source of operating potential and the cathode of which is connected to said second stationary contact, a conduction path through the silicon controlled rectifier being completed with said first switch means being operated to its second position wherein said second movable contact engages said second stationary contact to complete a path from the cathode of the silicon controlled rectifier to ground, and the gate of said silicon controlled rectifier comprising gating input thereof.

Claim 8

The combination according to claim 5 wherein said flying spot scanner includes at least one control grid for establishing the beam therein, the combination further including voltage divider means connected between a source of operating potential and a point of reference potential and having a tap thereon connected with said control grid; coupling means coupling the anode of said silicon controlled rectifier with a point on said voltage divider means to cause the potential applied to the control grid of said flying spot scanner to be at a first predetermined potential with said silicon controlled rectifier nonconductive and to be at a second predetermined potential sufficient to cut off the beam in said flying spot scanner with said silicon controlled rectifier being coNductive.

Claim 9

The combination according to claim 6 further including second switch means having a third movable contact coupled with said point of reference potential, and fourth and fifth stationary contacts, said second switch means normally closed with said third movable contact engaging said fourth stationary contact; means coupling said fourth stationary contact with said second movable contact of said first switch means; and means coupling said fifth contact with the second terminal of said capacitor so that operation of said third movable contact from said fourth contact thereof to said fifth contact causes said point of reference potential to be applied to the second terminal of said capacitor thereby discharging said capacitor irrespective of the position of said first switch means.

Claim 10

The combination according to claim 6 wherein said coupling means includes a transistor having collector, base and emitter electrodes, and a zener diode means; the collector of said transistor being coupled with said control grid and the emitter of said transistor being coupled through said zener diode means to said point of reference potential, the anode of said silicon controlled rectifier being connected to the emitter of said transistor; and means for establishing a predetermined bias on the base of said transistor to render said transistor conductive at less than saturation with said silicon controlled rectifier nonconductive and to render said transistor more conductive with said silicon controlled rectifier conductive.