Time dependent fluorescence measurements

An apparatus for collecting optical data pertaining to one or more characteristics of a sample, the apparatus comprising:

• a light source;
• one or more illumination optical elements for directing a light beam from the light source of a first frequency onto the sample;
• a scanner for scanning the light beam across the sample;
• and
• one or more collection optical elements for collecting light of a second frequency from the sample and transmitting the light to a detector, wherein none of the one or more collection optical elements are included among the one or more illumination optical elements, and wherein the first and second frequencies are different.

An apparatus for collecting optical data pertaining to one or more characteristics of a sample, the apparatus comprising:

• a light source;
• one or more illumination optical elements for directing a light beam from the light source onto the sample;
• a scanner for scanning the light beam across the sample;
• one or more collection optical elements for collecting light from the sample and transmitting the collected light to one or more detectors;
• and
• a first device that limits detection of light from the sample to light associated with a first vertical depth within the sample,
• a second device that limits detection of light from the sample to light associated with a second, different, vertical depth within the sample,
• wherein the first and second devices are collection optical elements.