Transcript Microscope 1: Forensic Microscopy

Forensic Microscopy
Microscope 1
Forensic Microscopy
• Generally takes one of six forms
depending on the type of evidence to be
examined
– Compound microscope
– Stereoscopic microscope
– Comparison microscope
– Polarizing microscope
– Microspectrophotometer
– Electron microscope
Compound Microscopes
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The “classic” microscope
Light is passed through object from beneath
Image is upside down and backwards
May possess a zoom magnification or multiple
lenses of varying strength
• Monocular and binocular versions
• Generally up to 1000x magnification
• Higher magnification limitations
– “Depth of focus” is decreased and creates focusing
challenge
– Cuts down on available light
Compound Microscopes
• Major
Components
– Eyepiece
– Tube
– Nosepiece
– Objectives
– Stage
– Focus
– Arm
– Base
Compound Microscopes
Comparison Microscopes
• Essentially two compound or
stereographic microscopes joined by a
“bridge”
• Vital for side by side comparison of two
pieces of evidence
• View can show either microscope or can
be “split” to show both at the same time
• Especially useful in ballistics and hair/fiber
cases
Comparison Microscopes
Stereographic Microscopes
• Most frequently used type of microscope in
forensics
• Light is passed either through an object or from
above
• Image is projected right side up and correct right
to left
• Usually the only method for opaque forms of
evidence
• Especially useful for soil analysis, entomology
and macroscopic evidence
• Magnification generally ranges from 2x to 125x
• Often called “dissecting” microscopes
Stereographic Microscopes
Polarizing Microscopes
• A special microscope application that outfits a
“normal” microscope with two devices (a
polarizer and an analyzer)
• The polarizer is used to impact incoming light
waves to reveal special properties of a material
• Affected light waves then pass through analyzer
before hitting the eye
• Especially useful in soil analysis (minerals) and
the identification of artificial fibers
Polarizing Microscopes
Polarizing Microscopes
Polarizing microscope view a a thin
slice of granite
Blemish on an LCD screen
visible in polarized light (right) but
not in normal visible light (left)
Electron Microscope
• Unique in that it uses a beam of electrons
aimed at the object
– Does not use light
• Extremely high magnification possible
– Ranging from 10x – 100,000x
• Can also be used as a spectroscope in
some applications
• Useful in gunshot residue cases
• Very expensive
Electron Microscope
Electron Microscope
Electron microscope
Electron microscope
Microspectrophotometer
• A beam of light is aimed at the object and
its spectrum can be collected
• The specific spectrum will be unique to
particular chemicals, fibers, etc.
• Spectral “fingerprints” can then be used to
determine specific matches between
different evidence samples
Microspectrophotometer
Microspectrophotometer