Department of Bioengineering, George Mason University, Fairfax, Virginia.
Edward S Harkness Eye Institute, Columbia University Medical Center, New York, New York.
J Biophotonics. 2018 Jun;11(6):e201700278. doi: 10.1002/jbio.201700278. Epub 2018 Feb 26.
A frequency-domain, non-contact approach to photoacoustic microscopy (PAM) that employs amplitude-modulated (0.1-1 MHz) laser for excitation (638-nm pump) in conjunction with a 2-wave mixing interferometer (532-nm probe) for non-contact detection of photoacoustic waves at the specimen surface is presented. A lock-in amplifier is employed to detect the photoacoustic signal. Illustrative images of tissue-mimicking phantoms, red-blood cells and retinal vasculature are presented. Single-frequency modulation of the pump beam directly provides an image that is equivalent to the 2-dimensional projection of the image volume. Targets located superficially produce phase modulations in the surface-reflected probe beam due to surface vibrations as well as direct intensity modulation in the backscattered probe light due to local changes in pressure and/or temperature. In comparison, the observed modulations in the probe beam due to targets located deeper in the specimen, for example, beyond the ballistic photon regime, predominantly consist of phase modulation.
本文提出了一种基于频域的、非接触式的光声显微镜（PAM）方法，该方法采用调幅（0.1-1MHz）激光作为激励源（638nm 泵浦光），结合双波混频干涉仪（532nm 探测光）实现对样品表面光声波的非接触检测。锁相放大器用于检测光声信号。本文展示了组织模拟体、红细胞和视网膜血管的成像结果。泵浦光的单频调制直接提供了与图像体积的二维投影等效的图像。位于表面的目标会由于表面振动产生表面反射探测光的相位调制，以及由于局部压力和/或温度变化产生背散射探测光的强度调制。相比之下，对于位于样品深处的目标（例如，超出弹道光子区域），探测光中的观察到的调制主要是相位调制。
