Transmission mode imaging.

The sample is illuminated through the probe, and the light passing through and interacting with the sample is collected and detected.

Reflection mode imaging.

The sample is illuminated through the probe, and the light reflected from the sample surface is collected and detected.

Collection mode imaging.

The sample is illuminated with a macroscopic light source from the top or bottom, and the probe is used to collect the light from the sample surface.

Illumination/collection mode imaging.

The probe is used for both the illumination of the sample and for the collection of the reflected signal. Detection of the collected light can be achieved with a wide variety of instruments: an Avalanche Photo Diode (APD), a Photomultiplier Tube (PMT), an InGaAs Detector, a CCD, or a spectrometer. The signal obtained by these detectors is then used to create an NSOM image of the surface.