Transcript Chapter 7 The Microscope

CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
1 7-
 1. Ocular lens
 2.Revolving nosepiece
 3. Lower power
objective
 4. Medium power
objective
 5. High power objective
 6. Stage clips
 7. Diaphragm
 8. Light source
(illuminator)
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
2 7-
 9. Eyepiece
 10. Arm
 11.Stage
 12. Coarse
Adjustment
 13. Fine Adjustment
 14. Base
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
3 7-
 1. Ocular Lens: Lens within the eyepiece
 2. Revolving Nosepiece- contains the
objective lens
 3. Objective Lenses: lens directly over
specimen; low, medium and high power
 4.Stage- supports slide
 Stage clips- secures slide on stage.
 5. Diapraghm (condenser)- focuses light on
specimen
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
4 7-
 6. Light source (illuminator)- source of artificial
light
 7. Arm: upright structure which supports
microscope
 8. Base: Supports microscope
 9. Body tube: allows light can pass through to go to
each lens
 10. Coarse Adjustment: focus an image under low
power
 11. Fine Adjustment: focuses an image under
medium and high power
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
5 7-
Compound Light Microscope
 How is it used?
 Light passes through translucent specimen to view
internal structures.
 When is it used?
 On translucent or thin specimens.
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6 7-
The Compound Microscope
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
7 7-
The Comparison Microscope
How is it used?
 Two independent objective lenses joined
together by an optical bridge to a common
eyepiece lens.
 Can view two different items
simultaneously
When is it used?
 Firearms examination
 Trace evidence (hair, fibers, etc)
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8 7-
The Stereoscopic Microscope
How is it used?
 Two monocular compound microscopes
 Three-dimensional image of a specimen
 Use both eyepiece lenses
When is it used?
 Evidence not requiring very high
magnification (10x–125x)
 Microscopic examination of big, bulky items
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
9 7-
The Microspectrophotometer
How is it used?
 Spectrophotometer coupled with a
light microscope.
 Can simultaneously obtain the visible
absorption spectrum or IR spectrum
of the material being observed
When is it used?
 Trace evidence, paint, fiber, and ink
evidence.
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
10 7-
The Scanning Electron Microscope
How is it used?
 (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
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
11 7-
 When is it used?
 Get a very magnified image
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
12 7-
Dental Plaque
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
13 7-
Bread Mold
Aspergillus sp.)
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14 7-
Penecillium sp.
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
15 7-
SEM: Hair and Hair follocles
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
16 7-
SEM: hafnium nitride interface
coating on carbon fibers
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
17 7-
Dust Mite
Family Reunion
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
18 7-
Important Terms
 Field of View: area of specimen that can be
seen after its magnified
 Depth of Focus: thickness of specimen
entirely in focus under microscope
 Polarizer: devise that permits the passage
of light waves vibrating in only one plain.
 Parafocal: can change objective lens and
field of view will remain in focus
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
19 7-
 Monocular: microscope with one
eyepiece
 Binocular: microscope with two
eyepieces
 Virtual Image: image that is
magnified (cannot see it directly)
 Real image: image seen directly
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
20 7-
 5. What happens to a compound microscopes field of
view when you increase the magnification?
 Field of view decreases
 6. When using a comparison microscope why is it
important to closely match the optical characteristics?
 Ensure both specimens are seen at equal magnification
and with minimal but identical lens distortions.
 7. What is the most frequently used and versatile
microscope found in the crime lab? List 3 reasons why
this type is so widely used
 Stereoscopic microscope because of wide field of view,
great depth of focus, large working distance
CRIMINALISTICS
An Introduction to Forensic Science, 9/E
By Richard Saferstein
PRENTICE HALL
©2007 Pearson Education, Inc.
Upper Saddle River, NJ 07458
21 7-