MSI vs TIR

This week we read up a little bit more on Multispectral images (MSI) and total internal reflection images (TIR). The way that these MSI scanners are programmed is that they integrate both the capabilities of MSI and TIR images when the user places his or her finger on the scanner. The multispectral images are processed to enhance the fingerprint minutiae. Both MSI and TIR images are then passed into the the SDK for the scanner to detect the minutiae in the fingerprint.

Similarities:

1. Light Source - provides the light for our sensor to illuminate the platen on top of which the finger rests.
2. Imaging System – creates the digital imaging array from the image pn the platen.

Differences:

• MSI - The orientation of the light source and imagers do not exceed any critical angle conditions.
• TIR – In normal TIR sensors, the light strikes a medium larger than the critical angle.
• MSI - Has multiple illumination wavelengths,
• TIR - Monochromatic illumination system.
• MSI - uses polarizers that are arranged orthogonally to highlight the light that penetrates the skin surface. Once the light penetrates the skin surface, it undergoes multiple scattering events, once the light exits the skin it makes its way to the image array

Full Research Description of this is found in the following papers:

1. Multispectral Fingerprint Biometrics

2. Fingerprint enhancement using a multispectral sensor