1. 7-1 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 1 THE MICROSCOPE

2. 7-2 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 2 Introduction Microscope: optical instrument, uses a lens or a combination of lenses to magnify and resolve fine details of an object. Earliest methods for examining physical evidence relied solely on microscope.

3. 7-3 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein Two Types of Images Virtual image : magnified image seen by looking through a lens Real image: image viewed directly 3

4. 7-4 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 4 The Compound Microscope objective lens: lower lens eyepiece (ocular) lens: upper lens Total magnification: calculated by multiplying power of objective lens times power of eyepiece lens.

5. 7-5 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein We will learn about serveral types of microscopes : Compound microscope Stereoscopic microscope Comparitive microscope Microspectrophotometer Scanning electron microscope (SEM) 5

6. 7-6 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 6 The Compound Microscope The Mechanical System –Stage: plate on which specimens placed. –Coarse Adjustment: knob used to focus microscope lenses by moving body tube. –Fine Adjustment: knob used to focus lenses by moving body tube, but by much smaller magnitude.

7. 7-7 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 7 The Optical System –Illuminator: artificial light, usually supplied by light bulb, to illuminate specimen. –Condenser: lens system under microscope stage, focuses light onto specimen. –Diaphragm: controls amount of light passing through specimen –Objective Lens: lens closest to specimen; usually several objectives mounted on revolving nosepiece. (4X, 10X, 40X) –Eyepiece/Ocular Lens: the lens closest to the eye. (10X) The Compound Microscope

8. 7-8 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 8 The Comparison Microscope till 1:43 till 1:43 two independent objective lenses joined together by an optical bridge to a common eyepiece lens. objects under investigation are observed side-by-side in circular field that is equally divided into two parts. Modern firearms examination began with introduction of comparison microscope, with ability to give firearms examiner a side-by-side magnified view of bullets.

9. 7-9 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 9

10. 7-10 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 10 Bullet comparison Hair comparison

11. 7-11 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 11

12. 7-12 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 12 The Stereoscopic Microscope two compound microscopes aligned to present three- dimensional image of specimen, look through both eyepiece lenses. useful for evidence not requiring very high magnification (10x-125x). large working distance makes it quite applicable for the microscopic examination of big, bulky items.

13. 7-13 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 13 The Microspectrophotometer how it works how it works spectrophotometer (measures light intensity of specific wavelengths / color) coupled with a light microscope. examiner can simultaneously obtain the visible absorption spectrum or IR (infrared) spectrum of material being observed. especially useful in examination of trace evidence, paint, fiber, and ink evidence.

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15. 7-15 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 15

16. 7-16 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 16 The Scanning Electron Microscope images images bombards a specimen with a beam of electrons, produces highly magnified image up to 1 million X. Its depth of focus is some 300 times better than optical systems at similar magnification.

17. 7-17 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein SEM With the SEM, we can tell if the car lights were ON or OFF when the light was broken in an accident. Why might that be important? 17

18. 7-18 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein 18

19. 7-19 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein Advantages and disadvantages of different types of microscopes 19 Pros: inexpensive and easy to use Compound Light Microscope Pros: allows the side by side viewing of 2 objects Comparison Microscope Pros: also inexpensive and easy to use, and in full color, 3 D Stereoscopic Microscope Pros: can scan trace evidence Microspectrophotometer Pros: shows fine detail of extremely tiny objects SEM

20. 7-20 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 FORENSIC SCIENCE An Introduction By Richard Saferstein Disadvantages Cons: Expensive 20 Comparison 2K Microspectrophotometer 22K SEM Cons: Can be difficult to prepare slides Compound Microscope SEM