Fig. 1.

Custom-made NIR confocal reflectance combined with two-photon fluorescence apparatus. The figure shows the NIR laser light (in red) that is first scanned by two galvanometric mirrors (scanning head), then expanded by a telescope (SL and TL), and finally focused by the objective onto the specimen. The emitted light is separated from the exciting beam by a first dichroic mirror (DM1) and then split by a second dichroic mirror (DM2). Two photomultipliers detect the split fluorescence emissions (PMT1 and PMT2). A polarization beamsplitter (PBS) along with a quarter waveplate is used to direct the descanned reflectance confocal signals to an avalanche photodiode (APD) module with a point spread function size pinhole (PH) in front. The black arrows highlight the status of polarization light in forward and backward direction.