Greenough Design
Definition
A stereo microscope in which two completely independent objective lenses, tilted at the convergence angle, each with its own optical axis, form the stereoscopic image pair. Provides strong depth perception; limits NA.
- Type
- Stereo microscope optical design
- Structure
- Two independent objective lenses at convergence angle
- Strength
- Strong depth perception
- Limitation
- Limits numerical aperture (NA)
Common questions
How does the Greenough design differ from the common main objective (CMO) stereo design?+
The Greenough design uses two separate, independently tilted objective lenses to form the two images, while a CMO design shares a single large front objective lens for both eyepiece paths, which generally gives a more parallel, less distorted image and easier accessory attachment than Greenough optics.
Why might an examiner prefer a Greenough design despite its NA limitation?+
The tilted dual-objective arrangement produces a strongly three-dimensional image that is useful for judging surface relief and depth on toolmarks or trace evidence, and the design is typically more compact and lower-cost than a CMO instrument of comparable magnification.
Related terms
- 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...
- Class Characteristics
- Features deliberately or systematically imparted to a group of items by design or manufacture, such as the calibre of a bullet, the...
- 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...
- Comparison Microscope
- Two compound microscope bodies connected by an optical bridge that presents one half of each body's image in a single split eyepiece...
- Congruent Matching Cells (CMC)
- An objective, measurement-based metric for cartridge-case comparison developed at NIST, quantifying the fraction of surface topography cells showing high correlation between questioned...
- Individual Characteristics
- Surface features on a fired bullet or cartridge case that arise from random or unique events (tool wear, corrosion, service damage) and...
- Medullary Index
- The ratio of the medulla diameter to the total hair shaft diameter. In companion animal hair identification, a medullary index above 0.5...
- Optical Bridge
- The beam-splitter and prism assembly that couples the two microscope bodies of a comparison microscope and produces the split-field composite image in...
- Parfocal Stage
- A microscope stage on which the specimen remains approximately in focus when switching between objectives, enabling rapid survey across magnification ranges without...
- PCAST 2016
- President's Council of Advisors on Science and Technology 2016 report 'Forensic Science in Criminal Courts', which assessed foundational validity of forensic disciplines...
- Stereo Microscope
- A low-magnification microscope producing stereoscopic depth perception by presenting each eye with a slightly different viewing angle (convergence angle 10-15 degrees). Uses...