Patents by Inventor Stefan Borejko

Stefan Borejko has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 4052644
    Abstract: An electronic flash unit having the conventional flash tube, storage capacitor dischargeable through the flash tube, measuring device for recording the quantity of light emitted by the flash tube and reflected back from the subject being photographed, a pulse generator responsive to the measured reflected light, and means for quenching the flash in response to a pulse produced when the measured reflected light reaches a threshold value. The present flash unit, in addition to the conventional features just mentioned, includes the novel feature of a light-emitting diode which becomes illuminated when the light measuring means and the pulse generator circuit become operative, thus signalling to the user of the device that the so-called "computer" mechanism has actually operated. Circuit means is provided for extinguishing the light-emitting diode at the proper time.
    Type: Grant
    Filed: March 15, 1976
    Date of Patent: October 4, 1977
    Assignee: Rollei-Werke Franke & Heidecke
    Inventor: Stefan Borejko
  • Patent number: 4028613
    Abstract: An arrangement for supplying a load with controlled current of a predetermined voltage which remains uniform notwithstanding variations in voltage of the alternating current supply, and notwithstanding differences in the frequency of the alternating current supply. A monostable trigger stage of the switch mechanism is connected to a DC voltage which is proportional to the voltage of the alternating current source, and its resistor which is connected with the capacitive coupling of the trigger stage transistors and determines the reset time of the trigger stage, is connected to a constant DC voltage. The mechanism includes a voltage divider, the division ratio of which is variable by means of a frequency recognition circuit.
    Type: Grant
    Filed: March 26, 1976
    Date of Patent: June 7, 1977
    Assignee: Rollei-Werke Franke & Heidecke
    Inventors: Armin Stiller, Stefan Borejko
  • Patent number: 3998534
    Abstract: An electronic flash unit for photographic purposes, in which there is a first thyristor in series with the flash tube, and a second thyristor which, in series with a quenching capacitor, is in parallel with the first thyristor. The first thyristor is quenched at the appropriate time, by quenching current from the quenching capacitor, and after the first thyristor has been rendered non-conductive, the second capacitor is also rendered non-conductive by forced commutation. The arrangement shortens the recovery time of the apparatus, as compared with prior art apparatus of this same general type, to such an extent that the flash apparatus may be used with a motion picture camera as well as a still camera, to produce one or more flashes during each shutter-open cycle of the motion picture camera.
    Type: Grant
    Filed: April 1, 1975
    Date of Patent: December 21, 1976
    Assignee: Rollei-Werke Franke & Heidecke
    Inventors: Axel Schulze, Stefan Borejko