Zeiss LSM 510 Manual

Also see for LSM 510: Quick start

LSM 510 ANNEXLSM 510 META Monitor Diode Carl Zeiss03/06 B 45-0021 e 8-19Application examples:a) Checking the laser powerThis function is not automated so far. Toqualitatively measure the laser power, the diodecan be used in such a way that the gray levelobtained in the Line Scan mode at a certainsetting of the whole system is stored as a textoverlay together with the image (manually done byuser). As the diode setting (Ampl. Gain, Ampl.Offset, ND filter) is stored together with the image,the setting is automatically reloaded when usingthe REUSE button. If deviations can be observed itis easy to set the laser power to the old value bymeans of the AOTF transmission.b) Noise Reduction by RatioContrary to the PMT signal, the signal of themonitor diode is not modulated by any specimeninformation. Thus it can be used to ratio the PMTsignal to get rid of the laser noise (due to any laseras a physical fact) and thereby improve the signalto noise ratio of the fluorescence or reflectanceimage. The major condition which has to befulfilled to use the monitor diode for this purposeis that the dominating source of noise is lasernoise. The signal of the monitor diode will alwaysbe dominated by laser noise (independent of thepower set at the laser, or the transmission set atthe AOTF), whereas the dominating source ofnoise in the PMT signal can also be the shot noiseof light (shot noise especially occurs in low lightfluorescence application; as rule of thumb it can benoted that the shot noise is limiting the signal tonoise ratio, if the PMT voltage has to be set to avalue > 400 V).Any kind of noise which can not be observed in both channels at a time will be amplified andnot reduced by the ratio process. Low or high frequency laser noise is the only source of noisewhich is correlated in the PMT signal and the signal of the monitor diode.Low or high frequency laser noise is mainly introduced if the Ar lasers are used at a tube current lowerthan 8 A (Ar-Vis) or 20 A (Ar-UV) respectively.Fig. 8-6 Scan Control window