A control system of an intensified video camera dedicated to numerical storage of multi-exposed images

Abstract

This paper describes a control system developed for acquisition of sequences of multi-exposed images, the goal being acquisition of quantitative information from flow visualizations obtained by laser tomography. The basic equipment consist of a camera equipped with a light intensifier and an electronic shutter. The video signal of the camera is digitized by an IBM personal-computer-compatible frame-grabber. The control system is designed to synchronize the activity of the different equipments of the process: camera, shutter, frame-grabber and flow generator. Different parameters can be defined: number of images to be acquired, number of expositions, each exposure and shut-down time, delay between flow generation and image acquisition. These process parameters are transmitted through a serial line by a program developed in the Windows environment. For one frame, exposure and shut-down times can be defined with a precision of 1 mu s. These different times are generated by a sequencer obtained with programmable logical devices. The system is not specific to fluid mechanics; it can be used for quite a lot of problems that show rapid changes.

High-speed video acquisition system applied to flow study

“…The synchronization module controls the number of images (1 to 256) for each sequence and allows three exposure modes (figure 6) (Fouquet et al 1994). For these modes, we use the full integration period of the sensor authorized by the camera.…”