Comparison Microscope
Definition
Two compound microscope bodies connected by an optical bridge that presents one half of each body's image in a single split eyepiece field, allowing simultaneous side-by-side visual comparison of questioned and known specimens.
- Inventor
- Calvin Goddard (1925)
- Key feature
- Two stages and two objectives joined by an optical bridge that merges both images into a single split eyepiece field; dual-stage rotation aligns striations
- Primary applications
- Fired bullets, cartridge cases, tool-marks, firearm marks
Common questions
What is a comparison microscope used for?+
A comparison microscope is the standard tool for examining fired bullets, cartridge cases, and tool-marks in forensic investigations. It lets analysts view two specimens side by side in a single eyepiece to check if striations, marks, and surface features match.
How does a comparison microscope show two objects at once?+
Two compound microscopes are connected by an optical bridge that merges the images into one split eyepiece field. You see both the questioned specimen and the known specimen simultaneously in a divided view, making direct side-by-side comparison straightforward.
What magnification range does a comparison microscope typically use?+
Most comparison microscopes operate between 10x and 40x magnification. This range is standard for forensic work on ballistics evidence and tool-marks.
Related terms
- Class Characteristics
- Features deliberately or systematically imparted to a group of items by design or manufacture, such as the calibre of a bullet, the...
- Individual Characteristics
- Surface features on a fired bullet or cartridge case that arise from random or unique events (tool wear, corrosion, service damage) and...
- AFTE Theory of Identification
- The Association of Firearm and Tool Mark Examiners' standard (1992, revised 2011) for reporting tool-mark comparison conclusions as Identification, Inconclusive, or Elimination...
- Rifling
- The helical groove pattern cut into a firearm barrel that imparts spin to the bullet, stabilising it in flight. Rifling lands and...
- ACS (Algorithmic Comparison Score)
- Extension of CMC that converts the raw cell-count score into a likelihood ratio using calibrated probability distributions from known match and non-match...
- AFTE Conclusion Scale
- Association of Firearm and Tool Mark Examiners scale: identification, inconclusive (subdivided A, B, C), elimination, unsuitable. The court-admissible vocabulary.
- BalliScan 3D
- Foster and Freeman's three-dimensional topographic bullet comparison instrument that maps striated surfaces using structured-light interferometry for both optical and digital comparison workflows.
- Blind Verification
- The procedure in which a second fingerprint examiner independently performs the Analysis and Comparison stages without knowledge of the first examiner's conclusion....
- Breech Face
- The forward surface of the bolt, slide, or breech block that seals the chamber and contacts the cartridge case head during firing....
- Cartridge Case Markings
- Impressions left on a fired cartridge case by the breech face, firing pin, extractor, and ejector of the firearm. Like rifling marks...
- CMC (Congruent Matching Cells)
- NIST algorithm that divides two 3D surface topography maps into cell grids and counts cells meeting quantitative topographic-correlation, slope-agreement, and height-offset criteria;...
- CMO Design
- Common Main Objective stereo microscope design using a single large objective with two off-axis optical channels passing through it. Allows better working...
Explained in these topics
- Ballistics Evidence in Wildlife PoachingA paired microscope system that displays two specimens (typically an evidence bullet and a test bullet) in a split field simultaneously, allowing a direct side...
- Bullet Striation Comparison and the Comparison MicroscopeA two-stage optical instrument with an optical bridge that presents the images of two specimens side by side in a single eyepiece, allowing direct visual compa...
- Forensic Examination of Firearms, Bullets, Shells and CartridgesTwo stages, two objectives, one optical bridge merging the two images into a single split eyepiece field. Invented by Calvin Goddard in 1925. Standard magnific...
- Microscopy for Forensic Science: Polarizing, Comparison, Stereoscopic, Fluorescent and ElectronTwo compound microscopes joined by an optical bridge so the analyst sees both fields in one split image. Standard tool for fired bullets, cartridge cases and t...
- Stereo Microscope and Comparison MicroscopeTwo compound microscope bodies connected by an optical bridge that presents one half of each body's image in a single split eyepiece field, allowing simultaneo...
- Tool-Mark Comparison Microscopy and 3D ImagingTwo microscopes joined by an optical bridge that places the two specimen images side-by-side in a single visual field; the primary tool for tool-mark and firea...