Editing Plate reader (section)

===Fluorescence===
Fluorescence intensity detection has developed very broadly in the microplate format over the last two decades. The range of applications is much broader than when using absorbance detection, but the instrumentation is usually more expensive. In this type of instrumentation, a first optical system (excitation system) illuminates the sample using a specific wavelength (selected by an optical filter, or a monochromator). As a result of the illumination, the sample emits light (it fluoresces) and a second optical system (emission system) collects the emitted light, separates it from the excitation light (using a filter or monochromator system), and measures the signal using a light detector such as a [[photomultiplier]] tube (PMT). The advantages of fluorescence detection over absorbance detection are sensitivity, as well as application range, given the wide selection of fluorescent labels available today.  For example, a technique known as [[calcium imaging]] measures the fluorescence intensity of [[calcium-sensitive dyes]] to assess intracellular calcium levels.<ref>{{cite journal |last1=Lin |first1=Kedan |last2=Sadée |first2=Wolfgang |last3=Mark Quillan |first3=J. |title=Rapid Measurements of Intracellular Calcium Using a Fluorescence Plate Reader |journal=BioTechniques |date=February 1999 |volume=26 |issue=2 |pages=318–326 |doi=10.2144/99262rr02 |pmid=10023544 |doi-access=free }}</ref>