Autoconfocal microscopy with a cw laser and thermionic detection

Daryl Lim, Kengyeh K. Chu, Jerome Mertz
2008 Optics Letters  
We introduce an application of thermionic emission in a PMT photocathode. Because of the nonlinear dependence of thermionic emission on absorbed laser power, a conventional PMT is found to produce a virtual pinhole effect that rejects unfocused light at least as strongly as a physical pinhole. This virtual pinhole effect is exploited in a scanning transmission confocal microscope equipped with a cw laser source. Because the area of the PMT photocathode is large, signal descanning is not
more » ... and thermionic detection acts as a self-aligned pinhole. Our technique of thermionic-detection autoconfocal microscopy is further implemented with graded-field contrast to obtain enhanced phase-gradient sensitivity in unlabeled samples, such as rat hippocampal brain slices.
doi:10.1364/ol.33.001345 pmid:18552953 fatcat:aqrbdainkrh55dc7ik7e56elcq