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. Author manuscript; available in PMC: 2009 Oct 19.
Published in final edited form as: Laser Photon Rev. 2009 Feb 1;3(1-2):159–179. doi: 10.1002/lpor.200810031

Figure 2.

Figure 2

(online color at: www.lpr-journal.org) Mesoscopic Optical Imaging techniques. Confocal microscopy isolates reflected or fluorescent light from the focus of a scanning laser beam using a pinhole (black) in front of a detector (dark red). Two-photon microscopy exploits non-linear excitation of fluorescence at only the focus of a pulsed near infra-red laser beam. Optical coherence tomography compares the phase of a reference beam (black) to reflected light (red) to isolate signal reflecting from specific depths. Camera-based 2D imaging is sensitive only to superficial layers and contains insufficient information to create images of deeper tissues. Photoacoustic tomography uses a pulse of laser light to generate thermo-elastic waves from absorbers, which can be detected using ultrasound transducers (black). Laminar optical tomography measures light that has scattered to different depths within the tissue.