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1 Do Now: What are the parts of a microscope?. 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education,

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Presentation on theme: "1 Do Now: What are the parts of a microscope?. 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education,"— Presentation transcript:

1 1 Do Now: What are the parts of a microscope?

2 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. Today Students will Understand the structure and function of a basic microscope Utilize microscopes to see small differences in samples 2

3 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 3

4 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 4

5 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. A microscope is an optical instrument that uses a lens or a combination of lenses to magnify and resolve the fine details of an object. The earliest methods for examining physical evidence relied solely on the microscope. The magnified image seen by looking through a lens is known as a virtual image, whereas an image viewed directly is known as a real image. The object to be magnified is placed under the lower lens, called the objective and viewed through the upper lens, called the eyepiece. Various types of microscopes are used to analyze forensic specimens. 5

6 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. In the basic compound microscope, the object to be magnified is placed under the lower lens (objective lens) and the magnified image is viewed through the upper lens (eyepiece lens). The magnification of the image can be calculated by multiplying the magnifying power of the objective lens times the magnifying power of the eyepiece lens. The microscope is composed of a mechanical system which supports the microscope, and an optical system which illuminates the object under investigation and passes light through a series of lens to form an image of the specimen. 6

7 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 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. 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. 7

8 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 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. Condenser: lens system under the microscope stage that focuses light onto the specimen. 8

9 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. The Optical System Objective Lens: the lens closest to the specimen; usually several objectives are mounted on a revolving nosepiece. Parafocal: when the microscope is focused with one objective in place, another objective can be rotated into place and the specimen remains very nearly in correct focus. Eyepiece or Ocular Lens: the lens closest to the eye. Monocular: a microscope having only one eyepiece Binocular: a microscope having two eyepieces. 9

10 Do now: How is an object magnified by a microscope? What role does light play? 10

11 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. Today Students will Apply understanding of the structure and function of a compound microscope Utilize microscopes to see small differences in samples 11

12 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. Compare different samples 12

13 Do now: How are compound microscopes helpful in a forensic lab? 13

14 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. Today students will: Explain the structures and functions of : comparison microscopes, Stereoscopic microscopes, Polarizing microscopes and the Scanning Electron microscope. Be able to explain appropriate uses for each 14

15 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. The comparison microscope consists of two independent objective lenses joined together by an optical bridge to a common eyepiece lens. When a viewer looks through the eyepiece lens of the comparison microscope, the objects under investigation are observed side-by-side in a circular field that is equally divided into two parts. 15

16 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 16

17 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 17

18 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 18

19 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 19

20 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. Modern firearms examination began with the introduction of the comparison microscope, with its ability to give the firearms examiner a side-by-side magnified view of bullets. 20

21 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 21

22 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. Comparing patterns of markings on a bullet surface to the same kind of markings on a test-fired bullet can produce a bullet identification. Comparing unique markings created on a cartridge case by firing in a gun to markings on a test-fired cartridge case can result in a cartridge

23 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 23

24 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 24

25 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 25

26 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 26

27 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. The stereoscopic microscope is actually two monocular compound microscopes properly spaced and aligned to present a three-dimensional image of a specimen to the viewer, who looks through both eyepiece lenses. It is particularly useful for evidence not requiring very high magnification (10x–125x). Its large working distance makes it quite applicable for the microscopic examination of big, bulky items. 27

28 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 28

29 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 29

30 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. Makes possible the comparison of any two objects that can be brought within its field, which are seen in juxtaposition through a single eyepiece. Particularly useful to the technical expert who seeks to compare substances, surfaces or colors. Allows for accurate investigation and ocular demonstration before courts It is of great assistance to the examiner of disputed or suspect documents. It is especially well suited for: examination of inks, colors, erasures, changes, interlineations, and overwriting The comparison of disturbed and undisturbed paper surfaces, pen, and pencil points, the tint, texture, and condition of paper surfaces, the texture and quality of typewriter ribbons, written and printed characters, and type faces. 30

31 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. Light that is confined to a single plane of vibration is said to be plane-polarized. The examination of the interaction of plane-polarized light with matter is made possible with the polarizing microscope. Polarizing microscopy has found wide applications for the study of birefringent materials; materials that split a beam of light in two, each with its own refractive index value. The 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. 31

32 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 32

33 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. The microspectrophotometer is a spectrophotometer coupled with a light microscope. The examiner studying a specimen under a microscope can simultaneously obtain the visible absorption spectrum or IR spectrum of the material being observed. This instrument is especially useful in the examination of trace evidence, paint, fiber, and ink evidence. 33

34 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. Finally, the scanning electron microscope (SEM) bombards a specimen with a beam of electrons instead of light to produce a highly magnified image from 100x to 100,000x. Its depth of focus is some 300 times better than optical systems at similar magnification. The bombardment of the specimen’s surface with electrons normally produces X-ray emissions that can be used to characterize elements present in the material under investigation. 34

35 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 35 Pollen Grains

36 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. Fig. 5. Identification of specific features on the firing pin mark of four case heads (G.F.L. a and b, Whinchester c and d) shot by the same pistol (Beretta, model 98FS). Scale bar 500 μ m. 36

37 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. Fig. 2. Comparison of the images obtained respectively on the original ammunition and on its replica by bright field (a and b) and dark field (c and d) optical microscopy and scanning electron microscopy (e and f). 37

38 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved.

39 7- Criminalistics, 10e Richard Saferstein © 2011, 2007, 2004, 2001, 1998, 1995 Pearson Higher Education, Upper Saddle River, NJ 07458. All Rights Reserved. 1.What are the major characteristics on the comparison microscope? 2.What type of evidence would you analyze using a comparison microscope? 3.What are the major characteristics on the Stereoscopic microscope? 4.What type of evidence would you analyze using a Stereoscopic microscope? 5.What are the major characteristics on the Polarizing microscope? 6.What type of evidence would you analyze using a Polarizing microscope to? 7.What are the major characteristics on the Scanning Electron microscope? 8.What type of evidence would you analyze using a Scanning Electron microscope? 39

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