3D Optical Scanning
Definition
Non-contact surface topography measurement using structured light or white-light interferometry to produce a nanometre-resolution height map of the document surface; an alternative to ESDA for fragile or irreplaceable documents.
- Technology
- Structured light, white-light interferometry, or laser profilometry
- Contact method
- Non-contact (contact-free)
- Resolution capability
- Nanometre-level height mapping
- Primary applications
- Indented writing on documents and bite mark digitisation
Common questions
When would a forensic examiner use 3D optical scanning instead of ESDA for documents?+
3D optical scanning is a contact-free alternative to ESDA that works well with fragile or irreplaceable documents. Since it uses structured light or white-light interferometry to map the surface without touching it, there's no risk of damaging sensitive materials while still capturing detailed indented writing marks at nanometre resolution.
How does 3D optical scanning help with bite mark analysis?+
The technique digitises dental casts and bite mark impressions without contact, creating a precise 3D surface model. This model can then be compared directly to digitised photographs of bite marks or to other 3D scans, making it easier to assess consistency and match characteristics.
Is 3D optical scanning a contact-free process?+
Yes, 3D optical scanning is entirely contact-free. It uses structured light or laser profilometry to measure surface topography without touching the specimen, which protects fragile evidence and prevents any alteration or contamination.
Related terms
- ABFO No. 2 Scale
- The right-angle L-shaped reference scale with circular targets used in bite mark photography. Its design enables post-capture correction of lens distortion and...
- Birmingham Six
- Six men wrongly convicted in 1975 of the 1974 Birmingham pub bombings; their convictions were quashed in 1991 partly on the basis...
- Corona Wire
- A high-voltage wire in the ESDA instrument that deposits electrostatic charge uniformly over the Mylar surface; charge density is higher at points...
- Dental Cast
- A three-dimensional stone or resin model of a suspect's dentition made from an impression of their arches. The cast is the reference...
- Double-Swab Technique
- A collection method for dried biological stains in which a moistened swab rehydrates and lifts the stain from the surface, followed immediately...
- ESDA (Electrostatic Detection Apparatus)
- A non-destructive technique for detecting indented impressions on paper caused by writing pressure. A physical ink signature on paper produces detectable ESDA...
- ESDA Lift
- The permanent transparent Mylar sheet carrying the toner-developed image of the indented writing, produced by ESDA processing; suitable for court exhibition and...
- Foster+Freeman ESDA 2
- The current-generation commercial ESDA instrument (Foster+Freeman Ltd, Worcestershire, UK), used by the FBI Laboratory, DSTL (UK), Australian Federal Police, CFSL (India), and...
- Indented Writing
- Latent impressions produced in paper sheets beneath the writing sheet by the pressure of the pen tip; invisible under normal illumination but...
- Mylar Film
- A thin (approximately 6 micrometre) polyester film stretched over the document under vacuum in the ESDA process; it conforms to the document...
- PACE (Police and Criminal Evidence Act 1984)
- UK legislation governing police investigative powers, including the code of practice requiring audio (and later video) recording of police interviews, a reform...
- Sequence Evidence
- In ESDA casework, the determination of the relative order in which pages in a notepad were written, based on which impressions appear...
Explained in these topics
- Bite Mark Collection, Documentation and ComparisonContact-free digitisation of a dental cast or impression surface using structured light or laser profilometry. Produces a digital surface model that can be com...
- Indented Writing and the ESDA Electrostatic Detection ApparatusNon-contact surface topography measurement using structured light or white-light interferometry to produce a nanometre-resolution height map of the document su...