Abstract
We describe in this paper a DPIV system based on multispectral imaging. The system consists of three pulsed lasers, a
laser pulse combined system, a multispectral camera, a synchronizer and a computer with frame grabber. Wavelengths of
three pulsed lasers are 532nm, 650nm and 800nm. The laser pulses are combined together into the same beam path to
illumine the flow field. The beam splitting prism in the multispectral camera send the 532nm, 650nm and 800nm laser
pulses to three different CCD arrays respectively. The narrowband filters in front of the CCD arrays select specific
wavebands for every CCD. The three CCD arrays can work independently. They catch three images of the same area of
the flow field for different wavelengths at different moments in one exposure period. The synchronizer, which controls
the time sequence between the camera and lasers, has a time precision of 1ns and time step length of 50ns. To measure a
flow field, firstly, the synchronizer controls the camera to open shutter, then, it controls three lasers to generate laser
pulses at different moments in one exposure time to illumine the flow field. With this system we can get three particle
images at three certain moments set by the synchronizer in one exposure period (less than 0.14s). The system has been
validated in the lab and the result is also laid out in this paper. In this system, the time interval between different particle
images just depends on the pulse interval time of different wavelengths, and it is independent of the frame rate of the
camera, which is the most important advantage of this system. With different time intervals, this system can be used to
measure flow field with different speed level. And further more, by setting two different time intervals for a single
measurement, the system can be also used for high speed flow field with complicated structure measurement. Due to its
features, perspective of its appreciation should be wide.
