  We developed a multifocus optical-resolution photoacoustic microscope (MPAM)
with extended depth of field (DoF) by using a tunable acoustic gradient (TAG)
lens and a pulse delay method. TAG lens is designed to control the divergence
angle of the laser beam. Three fibers with different length are used to output
three laser pulses with different delay time. By controlling the fire time of
the laser pulses, we can get three focal spot through TAG lens in our system in
one A-line data acquisition. The DoF of MPAM measured using a vertically tilted
carbon fiber is about 775 micrometers. The lateral resolution is estimated to
be 2.8 micrometers. A phantom consists of tungsten wires and a zebrafish is
used to verify the large depth-of-field of our system.
