Imaging depth of acoustic resolution photoacoustic microscopy is capable of reaching the centimeter level. There are several drawbacks regarding to the mainstream illumination designs of current acoustic resolution photoacoustic microscopy systems, e.g. switch between bright field illumination and dark field illumination is not available, and the utilization efficiency of laser energy is very low. Therefore, the application of the system is limited. A novel optical illumination design has been proposed to overcome these limitations. A convex lens is applied to focus the diverging ring-shape light before it is reflected by the optical condenser, as a result, the ultimate laser spot on the sample surface can be smaller. The Monte Carlo simulation results show that laser fluence within the volume of effective ultrasound detection has been improved by as much as 6 times, and therefore the intensity of photoacoustic signals can be linearly increased as well. On the other hand, the tuning range of optical focus depth of the system has also been expanded, and after specific tuning, optimal photoacoustic signals can be obtained within different kinds of samples.