Fluorescence Microscope
Definition
Uses UV or short-wavelength excitation to make fluorophores emit longer-wavelength light. Used for semen, saliva, fibres and ink discrimination.
- Excitation
- UV or short-wavelength light
- Effect
- Fluorophores emit longer-wavelength light
- Trace evidence uses
- Semen, saliva, fibres and ink discrimination
- Instrument class
- Specialised optical microscope variant
Common questions
How does a fluorescence microscope discriminate between two fibres that look identical under normal light?+
Dyes and finishing treatments used in different fibre batches often fluoresce at different colours or intensities under UV excitation even when the fibres appear the same colour under white light, giving an additional comparison point that visible-light microscopy cannot provide.
Why is fluorescence microscopy useful for locating biological stains like saliva or semen on an item before sampling?+
Many biological fluids and stains fluoresce faintly under UV excitation, letting an examiner scan a large item and pinpoint small or dried stains that are invisible under ordinary lighting, guiding where to take a confirmatory swab or cutting for further testing.
Does fluorescence microscopy identify what a stain actually is, or only that something is present?+
It primarily helps locate and screen material by showing where fluorescence occurs, but identifying the specific substance, such as confirming semen or a particular ink, still requires targeted confirmatory chemical or biological tests beyond the fluorescence observation alone.
Related terms
- 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...
- Depth of Field
- Axial thickness of the specimen that appears acceptably in focus at one time. High in stereoscopic microscopes, very low in oil-immersion compound...
- EDX / EDXRF
- Energy-dispersive X-ray detector attached to an SEM. Identifies elements from characteristic X-rays emitted when the beam strikes the sample. Backbone of GSR...
- Numerical Aperture (NA)
- The product of the refractive index of the medium between objective and specimen and the sine of the half-angle of the maximum...
- Polarising Microscope
- Compound microscope fitted with a polariser below and an analyser above the stage. Used to study birefringent materials like fibres, minerals and...
- Resolution
- The ability of a mass analyser to distinguish two ions of nearly equal m/z, defined as m/Δm at a given peak. A...
- SEM
- Scanning electron microscope. Focused electron beam raster-scans the sample surface; resolution down to a few nanometres with great depth of field. Paired...
- Stereoscopic Microscope
- Two separate light paths producing a true 3D image at low magnification (typically 7x to 40x). Used for trace recovery, gross examination...
- TEM
- Transmission electron microscope. Electrons pass through an ultra-thin section; resolution below 1 nm. Rare in routine forensic casework, common in research.