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Flash-free high-speed video stroboscope

A novel video stroboscope for periodical and nonperiodical repetitive high-speed events has been developed, constructed and tested. The stroboscope does not utilize a flash light. The object can be illuminated by a standard CW light source such as a halogen lamp or by day light. Hence, self-luminous objects can also be examined. The system consists of an asynchronously shuttered progressive scan CCD camera, a frequency-independent digital phase shifter and a PCI-bus frame grabber. Both, the phase shifter and the frame grabber are located in the same Pentium computer. Optionally an universal counter and frequency synthesizer for control purposes can be added. The image of the stroboscopically investigated event is displayed live on the PC monitor. The shutter of the camera is triggered by the event via the phase shifter which can be programmed to change the phase shift slowly. In the case a slow motion effect can be realized in real time. The apparent speed of the displayed movement does not depend on the real event frequency. Both the phase shift and the slow motion period are selectable independent of the real event frequency. Non-periodical but repetitive events can be observed in an alternative time- delay mode of the phase shifter. The camera exposure time can be varied between 1.25 microsecond(s) and 16 ms. It allows the stroboscopic observation of very fast oscillating (above 10 kHz) and rotating (above 100,000 rpm) objects. Sequences of up to 300 frames each can be stored on the hard disc derive for documentation, evaluation and playback. Each frame has a maximum resolution of 659 X 494 pixel at 256 gray levels.