Spatial heterodyne scanning laser confocal holographic microscopy

摘要

Scanning laser confocal holographic microscopy using a spatial heterodynedetection method is presented. Spatial heterodyne detection technique employs aMach-Zehnder interferometer with the reference beam frequency shifted by twoacousto-optic modulators (AOM) relative to the object beam frequency. Differentfrom the traditional temporal heterodyne detection technique in which hundredstemporal samples are taken at each scanning point to achieve the complexsignal, the spatial heterodyne detection technique generates spatialinterference fringes by use of a linear tempo-spatial relation provided bygalvanometer scanning in a typical line-scanning confocal microscope or for theslow-scanning on one dimension in a point-scanning confocal microscope, therebysignificantly reducing sampling rate and increasing the signal to noise ratiounder the same illumination compared to the traditional temporal heterodynecounterpart. The proposed spatial heterodyne detection scheme applies to bothline-scanning and point-scanning confocal microscopes. In this paper, wepresent the mathematical principles of the spatial heterodyne detection methodand experimental schemes for both line-scanning and point-scanning confocalmicroscopes. Computer experiments are provided to demonstrate the validity ofthis idea. The presented spatial heterodyne scanning laser confocal holographicmicroscope (SH-SLCHM) can obtain both amplitude and quantitative phaseinformation of the object field without a significant increase in complexity ofoptical and electronic design on the basis of a traditional scanning laserconfocal microscope (SLCM). SH-SLCHM may find applications in opticalmetrology, in-vivo tissue imaging, and ophthalmic imaging.