A CONTROL-SYSTEM OF AN INTENSIFIED VIDEO CAMERA DEDICATED TO NUMERICAL STORAGE OF MULTI-EXPOSED IMAGES

This paper describes a control system developed for acquisition of seq uences of multi-exposed images, the goal being acquisition of quantita tive information from flow visualizations obtained by laser tomography . The basic equipment consist of a camera equipped with a light intens ifier and an electronic shutter. The video signal of the camera is dig itized by an IBM personal-computer-compatible frame-grabber. The contr ol system is designed to synchronize the activity of the different equ ipments of the process: camera, shutter, frame-grabber and flow genera tor. Different parameters can be defined: number of images to be acqui red, number of expositions, each exposure and shut-down time, delay be tween flow generation and image acquisition. These process parameters are transmitted through a serial line by a program developed in the Wi ndows environment. For one frame, exposure and shut-down times can be defined with a precision of 1 mus. 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.