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Passport examination by a confocal-type laser profile microscope.

Shigeru Sugawara¹

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.

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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.