1. Chapter 7 The Microscope

2. Introduction THE MICROSCOPE Optical instrument
Lens or combination of lenses
Magnify, resolve fine details
Earliest methods for examining physical evidence
Magnified image = virtual image
Image viewed directly = real image.
THE MICROSCOPE

3. The Compound Microscope

4. The Compound Microscope
Schematic diagram of stereoscopic microscope
Two separate monocular microscopes
Each has own set of lenses except for the lowest
Objective lens common to both microscopes

5. The Compound Microscope
The Mechanical System
Base: the support.
Arm: the C-shaped upright structure
Stage: the plate on which the specimens are placed
Body Tube: the hollow tube on which the objectives and eyepiece lenses are mounted
THE MICROSCOPE

6. The Compound Microscope
The Mechanical System
Coarse Adjustment: the knob used to focus the microscope lenses by moving the body tube
Fine Adjustment: the knob also used to focus the lenses by moving the body tube, but by a much smaller magnitude
THE MICROSCOPE

7. The Compound Microscope
The Optical System
Illuminator: artificial light, usually supplied by a light bulb, to illuminate the specimen.
Transmitted Illumination: when the light is directed up through the specimen from the base.
Vertical or Reflected Illumination: when the light comes from above and reflects off the specimen.
THE MICROSCOPE

8. The Comparison Microscope
Two independent objective lenses joined together by an optical bridge to a common eyepiece lens.
The objects under investigation are observed side-by-side in a circular field that is equally divided into two parts
Modern firearms examination
Began with the introduction of the comparison microscope
Ability to give the firearms examiner a side-by-side magnified view of bullets
THE MICROSCOPE

9. The Stereoscopic Microscope
Two monocular compound microscopes
Three-dimensional image of a specimen
Use both eyepiece lenses
Evidence not requiring very high magnification (10x–125x)
Large working distance
Microscopic examination of big, bulky items
THE MICROSCOPE

10. Polarizing Microscopy
Plane-polarized
Light that is confined to a single plane of vibration
Polarizing microscope
Examination of the interaction of plane-polarized light with matter
THE MICROSCOPE

11. Polarizing Microscopy
Wide applications for the study of birefringent materials
Materials that split a beam of light in two
Each with its own refractive index value
Determination of these refractive index data
Provides information that helps to identify minerals present in a soil sample or the identity of a man-made fiber.
THE MICROSCOPE

12. The Microspectrophotometer
Spectrophotometer coupled with a light microscope.
Can simultaneously obtain the visible absorption spectrum or IR spectrum of the material being observed
Trace evidence, paint, fiber, and ink evidence.
THE MICROSCOPE

13. The Microspectrophotometer

14. The Microspectrophotometer

15. The Scanning Electron Microscope
(SEM) bombards a specimen with a beam of electrons instead of light
Produces a highly magnified image from 100x to 100,0000
Depth of focus 300X better than optical systems at similar magnification
Bombardment of the specimen’s surface with electrons
Produces x-ray emissions
Characterize elements present in the material under investigation
THE MICROSCOPE

16. Dental Plaque

17. Bread Mold Aspergillus sp.)

18. Penecillium sp.

19. SEM: Hair and Hair follocles

20. SEM: hafnium nitride interface coating on carbon fibers

21. Dust Mite Family Reunion