Microscopic techniques

Types of Microscopes

1. Microscopy
Types of microscopes
Light microscopes –
UV, Dark field, Phase contrast, Fluorescent
and
Electron microscope.
Dr. S. PARTHASARATHY, M.Sc. (Agri)., Ph.D.
Assistant Professor (Plant Pathology)

3. Introduction
•Microscopyis any technique for producing visible images of
structures.
•A microscope is an instrument designed to make fine details
visible.
•Light Microscope
•Electron Microscope
•Scanning Probe Microscope

8. •Theopticalmicroscopeisatypeofmicroscope
whichusesvisiblelightandasystemoflensesto
magnifyimagesofsmallsamples.
•Opticalandilluminationsystemsareitsbasic
elements.

10. Types of light microscope
–Bright-field microscope
–Dark-field microscope
–Phase-contrast microscope
–Fluorescence microscopes

11. Bright field
•“normal” wide-field
illumination method
•bright background
•low contrast
Dark field
•an opaque disc is
placed underneath the
condenser lens
•scattered light
•dark background
•high contrast
(structural details)

12. Polarizing microscope Brightfield/ Darkfield
Stereo Microscope

14. Phase contrast
•Principle:Differentdensitiesandrefractive
indicesofdifferentpartsofcells.

16. Fluorescent microscope
•Fluorescent compound which absorbs light
at one wavelength and then emits light at
longer wavelength.

17. Epi-Fluorescence microscope with 3 filters 4
Semi Apochromatic objective lenses
Inverted Fluorescence Compound
Microscope
Inverted Microscopes have the condenser
and light source above the stage and the
objective lenses below.

18. SEM
Scannedwithanelectron
beam,andthereflected
(orback-scattered)beam
ofelectronsiscollected,
thendisplayedatthesame
scanningrateonacathode
raytube(similartoaCRT
televisionscreen).

19. TEM
Contrastsintheimageare
producedbydifferencesin
beamscatteringordiffraction
producedbetweenvarious
elements of the
microstructure.

20. Scanning electron microscopeTransmission electron
microscope
Morphology character Internal structure
Electron beams scan over the
sample
Electron beams pass through
the sample
Magnification 1,00,00 0X Magnification 5,00,000 X
Three dimensional black and
white images
Produce two dimensional black
and white structure
Based on scattered electrons or
produce images by detecting
secondary electron which are
emitted from the surface of the
sample
Based on the transmitted
electron two produce image

22. Scanning Probe Microscopy
•Generatesatopographicalmap,onanatomicscale,thatisa
representationofsurfacefeaturesandcharacteristicsofthe
specimenbeingexamined.
•Scanningtunnelingmicroscopy(STM),Atomicforce
microscopy(AFM),Near-fieldscanningopticalmicroscopy.
•Three-dimensionalmagnifiedimagesaregeneratedthat
providetopographicalinformationaboutfeaturesofinterest.

23. Scanning Probe Microscopy