Platen Glass
Definition
The flat transparent surface on which original documents are placed for scanning in a photocopier or flatbed scanner; contamination or scratches on the platen produce fixed-position marks in every copy made on that machine.
- Function
- Flat scanning surface for a photocopier or flatbed scanner
- Defect source
- Scratches or contamination on the surface
- Effect
- Fixed-position marks reproduced on every copy
- Use
- Linking a document to a specific machine
Common questions
Why are platen glass marks considered strong individualising evidence?+
Because a specific scratch or dust pattern appears at the same fixed position on every copy made on that particular machine until it is cleaned or the glass is replaced, so a matching mark pattern across two documents suggests they were copied on the same device.
What could cause a false negative when comparing platen glass marks between two documents?+
If the platen was cleaned, the glass replaced, or the questioned documents fed through an automatic document feeder rather than placed on the platen, the characteristic fixed marks may be absent even though the same machine was used.
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