Particle Image Velocimetry (PIV) measures whole velocity fields by taking two images shortly after each other and calculating the distance individual particles travelled within this time. From the known time difference and the measured displacement the velocity is calculated. Since the flow can be quite fast one has to avoid blurred images and that‘s one reason to use laser pulses. They are only 6-10 ns long and freeze any motion. The other reason is that only laser light can be focused into a thin enough light sheet so that only particles in that plane are imaged. Otherwise the scattered light from particles in other planes would make this measurement impossible. A special camera is utilized so that it can store the first image (frame) fast enough to be ready for the second exposure. The "dead" time between the frames when the camera is "blind" is very short down to 100 ns.
- Double Pulsed Laser - Two laser pulses illuminate these particles with short time difference.
- Seeding - The flow medium must be seeded with particles, droplets or bubbles
- Software - Data capture, evaluation and display are fast and easy to operate.
- CCD Camera - A fast frame-transfer CCD captures two frames exposed by laser pulses.
- Light Sheet Optics - Laser light is formed into a thin light plane guided into the flow medium.
- Timing Controller - Highly accurate electronics control the laser and camera(s).