  By using the optical design software Zemax, on the basis of geometric optics
and primary aberration theory, the optimal design method of collimating mirror
is discussed and proposed, which eliminates the influence of conical concave
acoustic lens on beam transmission. The lens system imaging before and after
the optimization of the calibration lens is simulated by numerical simulation:
from the simulation results, after the calibration mirror is optimized, the
spherical aberration of the system is greatly reduced,. The root mean square
radius of the spot under the 0 degree field of view changes from 993.842
micrometers to 8.091 micrometers, and the geometric radius changes from 1000.98
micrometers to 11.087 micrometers; the MTF curve is obviously improved, the
cut-off frequency is increased by nearly 15 times, and the MTF value of the
meridian direction and sagittal direction under the 0 degree field of view are
between 0.9 and 1; The proposed optimization method of the collimating mirror
has important theoretical guiding significance for the study of the large depth
of field photoacoustic microscopy imaging system.
