ABSTRACT
Photoacoustic microscopy (PAM) employs dark-field optical excitation, which illuminates the sample surface outside the acoustic sensing area, and high-frequency focused ultrasonic detection, which receives short-pulsed, laser-induced PA waves. PAM is a recently developed modality of PA imaging. Similar to other PA imaging technologies, PAM detects laser-induced ultrasonic waves to image the internal distribution of optical energy deposition in biological tissue. Therefore, PAM reveals physiologically specific optical absorption contrast. However, it differs from reconstruction-based PA tomography (PAT) in several aspects. First, PAM provides high spatial resolution by detecting the high-frequency components of the PA waves. Second, PAM optimizes for the signal-to-noise ratio (SNR) by employing an optical-ultrasonic confocal geometry. Third, PAM involves no inverse reconstruction algorithms. Fourth, PAM minimizes unwanted interferences by employing novel optical illumination design. The PAM system acquires an image by two-dimensional (2D) raster scanning over the object along a horizontal plane.
