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Published on: January 3, 2011
Passport examination by a confocal-type laser profile microscope
1Fourth Forensic Department, National Research Institute of Police Science, Kahiwanoha 6-3-1, Kashiwa, Chiba, Japan. sugawara@nrips.go.jp
Forensic Science International
|March 28, 2008
Summary
A new nondestructive method precisely measures passport film thickness using a confocal laser microscope. This technique effectively authenticates genuine passports and reveals connections among counterfeit ones.
Area of Science:
- Forensic Science
- Optical Metrology
Background:
- Passport security relies on verifying authenticity.
- Nondestructive methods are crucial for examining sensitive documents like passports.
Purpose of the Study:
- To develop and validate a precise, nondestructive method for measuring passport film thickness.
- To assess the method's effectiveness in distinguishing genuine from counterfeit passports.
Main Methods:
- Utilized a confocal-type laser profile microscope to scan passport films.
- Developed a proprietary algorithm to calculate film thickness from surface and interface profiles.
- Measured film thickness on 35 genuine and 80 counterfeit Japanese passports.
Main Results:
- Achieved intra-sample standard deviation of approximately 1 micrometer for film thickness.
- Genuine Japanese passport films measured between 31.95 and 36.95 micrometers.
- Demonstrated a likelihood ratio of 11.7 for authenticating genuine passports.
Conclusions:
- The confocal laser microscopy method is highly effective for nondestructive passport authentication.
- The method's precision allows for the identification of relationships among counterfeit passports.
- This technique provides valuable evidence for forensic investigations and crime analysis.
