An optical configuration is realized to obtain quantitative phase-contrast maps able to characterize particles floating in a
microfluidic chamber by interference microscopy. The novelty is the possibility to drive the sample and measure it
thorough the same light path. That is realized by an optical setup made of two light beams coming from the same laser
source. One beam provides the optical forces for driving the particle along the desired path and, at same time, it works as
object beam in the digital holographic microscope (DHM). The second one acts as reference beam, allowing recording of
an interference fringe pattern (i.e., the digital hologram) in an out-of-focus image plane. This work finds application in
the field of micromanipulation as, the devise developed allows to operate in microfluidic chambers driving samples
flowing in very small volumes. Recently, the field of optical particle micro-manipulation has had rapid growth, due to
Optical Tweezers development. A particle is trapped or moved along certain trajectories according to the intensity and
phase distribution of the laser beam used.
Here, particles freely floating are driven by optical forces along preferential directions and then analyzed by a DHM to
numerically calculate their phase-contrast signature. The improvement is that one laser source is employed for making
two jobs: driving and analyze the sample. We use two slightly off-axis laser beams coming from a single laser source.
The interference between them gives the possibility to record in real-time a sequence of digital holograms, while one of
the beam creates the driving force. By this method, a great amount of particles can be analyzed by a real-time recording
of DH movies. This allows one to examine each particle at time and characterize it. The optical configuration and the
working method are illustrated. Experimental results are shown for polymeric particles and in-vitro.