1. 7.1
The Microscope

2. Objectives List and understand the parts of the compound microscope
Define magnification, field of view, working distance, and depth of focus
Contrast the comparison and compound microscope
Understand the theory and utility of the stereoscopic microscope

3. The Microscope
Virtual image – a magnified image as seen through a lens
Real image – an image seen directly
Two lens for viewing
Objective
Eyepiece (Ocular)

4. 5 major types of microscopes
Used in viewing forensic specimens
Compound
Comparison
Stereoscopic
Polarizing
Microspectrophotometer

5. Compound Microscope
Illuminator = Transmitted illumination or vertical or reflected illumination
Condenser = Abbe is the most simple (collects light rays from the base)
Objective lens = Closest to the specimen and is parfocal
Ocular lens = Monocular or binocular

6. Numerical Aperture
The ability of the objective lens to resolve details into separate images instead of one blurred image
(which happens up close)
Magnification power offers
Field of view
Depth of focus

7. Comparison Microscope
Two compound microscopes side by side
Produces a circular field with the two halves reserved for the specimens
To compare bullets, cartridges, and opaque objects
Vertical illumination is used
To compare hairs or fibers
Transmitted illumination is used

8. Stereoscopic Microscope
Provides magnification from
10x to 125 x
Presents a 3 dimensional image
Image is right side up
Two monocular compound microscopes spaced and aligned to present a 3-D image

9. Stereoscopic cont. Most frequently used in the crime lab
Wide field of view
Great depth focus
Large working distance for specimens
Used for paint, soil, gunpowder residues, marijuana

10. Polarizing Microscope
Plane-polarized
Light which emerges from a crystalline substance and vibrates in only 1 plane
Polarizer
A device that polarizes light in this way
Contains an analyzer
A second type of polarizing crystal through which a polarized beam passes

11. Polarizing cont.
If analyzer and polarizer are at 90 degree angles then no light is seen
Makes a specimen readily distinguishable
Useful for birefringement minerals in the soil