Eastman-kodak Company

Other

Lenard M Metzger

William K Hickok

Robert B Johnson

A bipolar transistor logic circuit comprises an input terminal for receiving digital logic signals, an output terminal, an output driver including a current sink transistor and a current source transistor, and a control stage coupled between the input terminal and the output driver. When the control stage is nonconducting, the current source transistor is turned ON and the current sink transistor is turned OFF providing a first digital logic signal at the output terminal. When the control stage is conducting, the current source transistor is initially turned OFF and the current sink transistor is turned ON providing a second digital logic signal at the output terminal. If the output load does not provide the amount of current required by the current sink transistor, the current source transistor is turned ON by the control stage and provides the current sink transistor with collector current to prevent the sink transistor from saturating. In an embodiment providing a tri-state output capability, a second input terminal for receiving digital logic signals is coupled to the aforementioned control stage and to a second control stage. When both control stages are conducting, both the current source transistor and the current sink transistor are turned OFF. As a result, the output terminal is set to a high impedance state and neither provides current to nor withdraws from the output load.

High speed, non-saturating, bipolar transistor logic circuit

Power distribution circuitry for battery-powered apparatus having multiple energy-consuming loads, such as a camera having an electronic strobe flash unit and a film drive motor, enables the loads to be actuated independently without drawing battery current simultaneously. This limits peak battery current which can extend the useful life of the battery.

Battery-power distribution apparatus

Exposure control apparatus for a camera having an objective lens, an unregulated, fixed output flash device which, in the absence of ambient light, provides one-half stop of underexposure of a photographic subject located at the near limit acceptable image focus point of the lens, and a mechanism for automatically controlling an exposure in accordance with the intensity of the ambient light. In a flash exposure mode, the mechanism is operated to produce an exposure which, in the absence of artificial illumination, would provide one-half stop of underexposure of the photographic subject. The total exposure, flash plus ambient, is within .+-. one-half stop of a nominally correct exposure throughout the useable depth of field of the camera lens.

Exposure control apparatus for flash photography

A battery-powered DC to DC converter is operated dynamically in accordance with the condition of the battery so that an optimum compromise is made between the performance of the battery and the performance of the converter in an application such as charging an electronic strobe flash unit capacitor. A transformer has oppositely wound primary and secondary windings. A switching transistor, serially connected between the primary winding and the battery, interrupts battery current through the primary winding, which causes current to flow through the secondary winding to charge the flash unit capacitor. A voltage-sensing circuit senses the battery open-circuit voltage and the battery load voltage, which varies as a function of the open-circuit voltage and battery internal resistance. A bistable control circuit causes the switching transistor to interrupt the primary winding current when the battery load voltage decreases below a predetermined percentage of the battery open-circuit voltage so the load that the converter places on the battery varies dynamically as a function of battery condition.

DC to DC Converter adjustable dynamically to battery condition

Electronic strobe flash apparatus has first and second flashtubes which are fired alternately and repeatedly to produce a composite, extended light flash. A start pulse triggers the first flashtube to cause a first normally charged capacitor to discharge through a primary winding of a transformer, the first flashtube, and a second normally discharged capacitor, thereby firing the first flashtube and charging the second capacitor. The transformer is adapted to produce a flashtube trigger voltage across its secondary winding when current in its primary winding is interrupted. The second capacitor is smaller than the first capacitor so that the voltage across the second capacitor increases more rapidly than the decrease in voltage across the first capacitor during its discharge. When the difference between the voltages across the two capacitors decreases to a predetermined level, the current from the first capacitor is interrupted, which quenches the first flashtube and produces a voltage of a first polarity across the secondary winding that triggers the second flashtube. In response to triggering the second flashtube, the second capacitor discharges through the second flashtube and the primary winding, thereby firing the second flashtube. When the second capacitor is substantially discharged, current from the second capacitor is interrupted, which quenches the second flashtube and produces a voltage of a second polarity across the secondary winding that triggers the first flashtube. In response to triggering the first flashtube, the first capacitor discharges again, and the aforementioned operating cycle is repeated. A control switch, responsive to the occurrence of a predetermined exposure parameter, causes current from the second capacitor to bypass the primary winding to terminate the light pulses.

Energy-saving electronic strobe flash apparatus having dual flashtubes

A tracking control apparatus, for use with a rotating-head magnetic tape player, provides a tracking control head in fixed rotational association with a playback head so that both scan corresponding parallel paths across the width of the tape in fixed relationship with each other. By so mounting the tracking control head that it overlaps adjacent recorded tracks and senses periodic information included therein, the apparatus provides a control signal for driving a tape capstan servo without need for the additional control track usually required by such apparatus. The periodic information may be, for example, the horizontal sync of a video signal in the adjacent tracks; the control signal is then derived from a comparison of the respective amplitudes of such horizontal component from each track. Since the overlapping position of the tracking head is fixedly related to the tracking position of the playback head, the control signal is indicative of the tracking alignment of the playback head itself. By further mounting the tracking head on the playback head wheel, and by using the record head during playback for such purpose, a dynamic real-time tracking apparatus is provided which additionally dispenses with a separate tracking control head.

Overlap track servo for dynamic position correction in a rotary-head

The present invention departs from conventional concepts, involving the use of magnetic tape or the like, of color video signal recording by providing video signal recording and reproducing apparatus in which preferential dropout compensation is obtained without the use of special dropout compensation circuitry. A color video signal is down-converted in frequency to produce a video signal of a recordable frequency range with picture information at relatively low frequencies and color and sound information at relatively higher frequencies, respectively. Dropouts, therefore, affect the sound information first, the color information second, and the picture information last, as is preferable. In accordance with another aspect of the invention, time base error correction is obtained without the use of time base error correction circuitry by separating the luminance and chrominance signals and so down-converting each signal to a recordable frequency range that the luminance carrier and the chrominance carrier have the same frequency. Upon recording and playing back, time base variations, as may be caused by tape flutter, will then affect both carriers equally. After up-converting and recombining the luminance and chrominance signals to form the original video signal, the frequency spacing between the luminance carrier and the chrominance carrier will be independent of time base variations in the recording process and, therefore, have the same frequency spacing as the original video signal.

Color video signal recording and reproducing apparatus providing

A servo control system provides interactive correction for both tracking and time base errors in a signal reproduced by a rotating playback head from magnetic tape. A tracking control head overlapping adjacent slant tracks provides a signal to a capstan servo for correcting positional errors. Time base errors are corrected by controlling a head servo with respect to variations in the incoming signal time base sensed by the playback head. By mounting both heads on the same head wheel, the head servo control provided by the playback signal has an interactive effect on the tracking sensor: with the playback head wheel moving at the correct speed to eliminate time base error, the tracking sensor will 'pull' the tape into precise tracking alignment by adjustment of the capstan servo. With the tape and head replicating their exact counterpart speeds obtained during record, skew at the point of head switching is automatically eliminated.

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Rochester, NY, United States of America

Lenard M Metzger