Particle/Image Analyzer

The Oxford Laser VisiSizer DP, manufactured by Oxford Laser, United Kingdom, measures the size, shape and velocity of opaque and/or transparent particles.  The VisiSizer DP allows for non-intrusive measurement of size of drops, solid powders, opaque solutions and bubbles and provides analytical data and direct laser images of the spray.  The system consists of a high-resolution camera, double pulsing YAG laser, data analysis software, computer and control equipment. 

The VisiSizer system measures particle size and velocity distributions using Particle/Droplet Image Analysis (PDIA).  A laser is used to illuminate the region of interest from behind and shadow images of the subject droplets are taken with a digital camera.  The laser and camera are triggered so that a single laser pulse provides an instantaneous view of the subject during each frame capture. The known time delay between the double-pulsed laser/camera image acquisitions allows for a particle displacement-over-time direct calculation of velocity.

Due to the direct image acquisition technique of the VisiSizer system, it is possible to calculate the ‘sphericity’ of the droplets being measured as well as the size and velocity. Many drop size measurement techniques assume that droplets are spherical due to the liquid surface tension, while this is often a valid assumption, the VisiSizer system provides a method to deal with non-spherical droplets.

The VisiSizer is best suited for measuring opaque or dense sprays. Because of the imaging system, sprays with large droplets or non-spherical drops can also be reliably measured.

Measurement range: 1 – 10,000 µm.