Optical/ Metallurgical Microscopy

1. OPTICAL/METALLURGICA
L MICROSCOPY

2. LENS:
In optics, piece of glass or other transparent substance
that is used to form an image of an object by focusing
rays of light from the object.
A lens is a piece of transparent material, usually circular
in shape, with two polished surfaces, either or both of
which is curved and may be either convex (bulging) or
concave (depressed).
The curves are almost always spherical, i.e., the radius of
curvature is constant. A lens has the valuable property of
forming images of objects situated in front of it.
Cont…..

3. Single lenses are used in eyeglasses, contact lenses,
pocket magnifiers, projection condensers, signal lights,
viewfinders, and on simple box cameras.
More often a number of lenses made of different
materials are combined together as a compound lens in a
tube to permit the correction of aberrations. Compound
lenses are used in such instruments as cameras,
microscopes, and telescopes.
LENS:

4. LENS MANUFACTURING

5. PRINCIPLE OF IMAGE
FORMATION IN CASE OF
CONVEX LENS w.r.t DIFFERENT
OBJECT LOCATIONS

6. METALLURGICAL
MICROSCOPE
Metallurgical microscope unlike biological microscope
works on the principle of reflected light microscopy.
The metallurgical microscope is an important tool for
metallurgists, with the help of which fine structural details
can be studied.
Since the metallographic specimens are opaque to light,
the sample must be illuminated by reflected light. The
metallurgical microscope is therefore based on reflected
light principle.
It has to be appreciated that the biological microscope
works on transmitted light principle.

7. METALLURGICAL
MICROSCOPE
It is used to study the topographic or microstructural
features on polished and etched surface of
magnifications of 1 to 1500x.

8. PRINCIPLE OF IMAGE
FORMATION
Next

9. MAGNIFICATION OF MICROSCOPE
There are two types of lens systems in metallurgical
microscope (i) Objective & (ii) Eye-piece. The initial
magnifying power of objective & eye-piece is engraved
on the lens mount.
When a particular combination of objective & eye-piece is
used at the proper tube length, the total magnification is
equal to the product of the magnifications of the objective
& eye-piece.

10. FUNCTIONS OF OBJECTIVE & EYE-
PIECE
Objective lens is used to resolve the microstructural
details of the surface of a polished & etched metallic
specimen.
Eye-piece is used to magnify the resolved details of the
microstructure. It does not further resolve the
microstructural details.