Photoacoustic imaging technique is a hybrid biomedical imaging technique that combines the merits of ultrasonic and optical imaging modalities. When a pulsed light illuminates and spreads into biological tissues, targeted biomolecules absorb light, and finally acoustic waves are created via thermoelastic expansion. This process is called as photoacoustic (PA) effect. Finally, a conventional ultrasonic transducer detects the generated acoustic waves and volumetric PA images can be obtained. Particularly, OR-PAM can noninvasively provide label-free microscopic images such as oxy and deoxy-hemoglobin, melanin, and DNA/RNA in cell nuclei. Thanks to the key advantages, OR-PAM has been widely used to study oncology, neuroscience, label-free histology, dermatology, ophthalmology, and cardiology. Although OR-PAM is regarded as a promising high-resolution microscopic technique, there is a pressing need to develop a compact, fast, and cost-effective OR-PAM system while maintaining high SNRs for wide spread preclinical and clinical applications.