Footwear
How many individualizing characteristics are needed to say a print came from a shoe?
Bonus points (50pts): What is the court case (who v who) that stated footwear impression was reliable?
There is no set number - left to the discretion of an experienced and qualified examiner
Court case: State of Illinois vs Charles A. Campbell - 1991
What is a lathe versus a mill?
Both are machines used to manufacture tools. A lathe however is where the tool is rotating around the stationary cutting tool, while in a milling machine the tool is rotated in a circular direction (I think - please let me know if this is incorrect)
What are the two (2) primary factors that affect glass transfer and persistence?
The position of the person relative to the window and the nature of the clothing worn by the person
What is numerical aperture? Does your resolution increase with lower or higher N.A's?
NA is the measure of the light gathering ability of a lens. Higher NA increases resolution
Equation for resolution: R=0.61wavelength/NA
R=1.22wavelength/(NAobj + NAcond)
Which direction does the extraordinary and ordinary ray vibrate in relation to a plane?
E: within the plane
O: perpendicular to plane
What are the three (3) ways to add texture to mold surfaces?
1) Hand stippling
2) Acid etching
3) Sand blasting
What are the three (3) types of toolmarks and give one example of a tool that creates that type of toolmark?
Compression: pressed straight into the substrate, have good class but fewer individual characteristics (ex: hammer, pliers, punches)
Sliding/striated: slides or scraps across surface, have minimal class but good individual (ex: screwdrivers, pry bars, extrusion dies)
Cutting: combo of compression and sliding, good class and individual (ex: bolt cutters, wire cutters, shears/snips)
Define glass and the basic process of how flat glass is made
Inorganic product of fusion which has cooled to a rigid condition without crystallizing. Molten glass is rolled onto a bed of molten tin (RI greater on surface in contact with tin and also can fluoresce) and then cooled on an annealing lehr
Made of formers (i.e. SiO2), fluxes (i.e.Na2CO3), and stabilizers (i.e. CaO)
What are three (3) aberrations/issues when focusing light that can occur from an ideal lens?
Chromatic aberrations: focus for one wavelength can be slightly different than another
Spherical: rays of light that are off the optical axis of the lens are focused at different locations
Curvature of field: flat object perceived to be curved object
Image distortion: magnification is not constant across field of view (i.e. barrel versus pincushion)
What are the three (3) different sections in a uniaxial indicatrix and what RI's can you see?
1) Circular section: only see omega
2) Principal section: see omega and epsilon
3) Random section: see omega and epsilon prime
List the four (4) methods to manufacture molds
1) Hand milling/hand engraving: use of pantograph to transfer tread design to metal mold blank)
2) CAD-CAM: same as hand milling except computer controlled)
3) Casting: model of shoe made from metal/plastic/wood that is then coated with layer of metal and model is removed after cast sets)
4) Electrical discharge machine: electrode plate created in shape/size of sole design and then electrode causes erosion/burning of metal to form mold
Which direction do the marks on the grooves run in relation to the barrel? Which direction do the marks on the lands run in relation to the barrel?
Grooves = parallel (formed when hole is created in the barrel blank)
Lands: perpendicular (formed during the rifling)
What are the three (3) goals of microscopy?
1) Produce a magnified image of the specimen (magnification)
2) Separate details in the image (resolution)
3) Render details visible to the detector (contrast)
What is the role of a condenser?
Illuminates the sample with a cone of light, creates uniform illumination across the field of view, controls contrast, minimizes/eliminates stray light
How do you read the Michel-Levy chart? What are on the axes?
Retardation color on x axis, thickness on y, birefringence is the radial lines
List two (2) factors that may cause variation between impressions/prints and two (2) factors that may cause distortion of an impression/print
variation: contact factors such as angle of footwear to target surface, point of initial contact with target surface, amount and distribution of weight, amount of residue on footwear, condition of target surface
distortions: movements, double/multiple impressions, interference of other matter between footwear and target surface, target surfaces that are flexible/can change
What are two (2) fireformed impressions and what are two (2) non-fireformed impressions
Fireformed: firing pin impression, breechface impression, chamber mark
NonFF: extractor impression, ejector mark, magazine mark
What are the characteristics of a real versus virtual image?
Real: can be projected onto a screen/captured by film, appears inverted and on the opposite side of the object
Virtual: can't be projected onto a screen, appears right side up, on the same side as the object, occurs when the obj distance is shorter than the focal length (ex: magnifying glass)
What are the three (3) fundamental actions of Abbe's theory of image formation
1) Diffraction that occurs by the specimen
2) Collection of the diffracted orders by the objective
3) Interference of these orders to produce the image
Isogyre = black arms of the cross
Melatope = center of the cross
Isochromes = circular colors
What are the two (2) different cutting methods to make soles?
1) Die cutting: cookie cutter like, can cut either cured or uncured rubber
2) Wellman machine: blade that travels around template, only cuts uncured, calendered rubber
Level 1: General ridge pattern configuration and ridge flow
Level 2: Ridge characteristics and spatial arrangement
Level 3: Dimensional attributes of ridge such as path deviation, width, shape, pores, edge contour, incipient ridges, breaks, creases, scars, other permanent details
What are the six (6) different lenses and please draw them?
Bioconvex, planoconvex, + meniscus, - meniscus, planoconcave, bioconcave
What are the four (4) illumination planes in Kohler illumination?
What are the four (4) image planes in Kohler illumination?
Illumination: lamp filament, condenser aperture, back focal plane of the objective, eye point
Image: Field diagram, stage/specimen plane, intermediate image plane, retina of the eye
What are the six crystallographic systems? Define the angles and axes (i.e. is a equal to b or c, and are the angles 90 degrees or not)
Cubic: isometric - a=b=c, angles are 90degrees
Uniaxial: tetragonal - a=b which doesn't equal c, angles are 90 degrees
Uniaxial: hexagonal - a=b which doesn't equal c, angle between a and b is 120degrees
Biaxial: orthorhombic - a doesn't equal b or c, angles are 90
Biaxial: monoclinic - a doesn't equal b or c, one angle is not 90
Biaxial: triclinic - a doesn't equal b or c, all angles are not 90