High-speed video recording system using multiple CCD imagers and digital storage

This paper describes a fully solid state high speed video recording system. Its principle of operation is based on the use of several independent CCD imagers and an array of liquid crystal light valves that control which imager receives the light from the subject. The imagers are exposed in rapid succession and are then read out sequentially at standard video rate into digital memory, generating a time-resolved sequence with as many frames as there are imagers. This design allows the use of inexpensive, consumer-grade camera modules and electronics. A microprocessor-based controller, designed to accept up to ten imagers, handles all phases of the recording: exposure timing, image digitization and storage, and sequential playback onto a standard video monitor. The system is capable of recording full screen black and white images with spatial resolution similar to that of standard television, at rates of about 10,000 images per second in pulsed illumination mode. We have designed and built two optical configurations for the imager multiplexing system. The first one involves permanently splitting the subject light into multiple channels and placing a liquid crystal shutter in front of each imager. A prototype with three CCD imagers and shutters based on this configuration has allowed successful three-image video recordings of phenomena such as the action of an air rifle pellet shattering a piece of glass, using a high-intensity pulsed light emitting diode as the light source. The second configuration is more light-efficient in that it routes the entire subject light to each individual imager in sequence by using the liquid crystal cells as selectable binary switches. Despite some operational limitations, this method offers a solution when the available light, if subdivided among all the imagers, would not allow a sufficiently short exposure time.