fingerprint

Hi guys &gals,

Im in a new project to design a fingerprint scanner.. Please help me which sensor would be best to use in fingerprint scanner.. Capacitive sensor or optical sensor.. Its very much difficult for me to find ckt diagram/schematic for these sensor.. If anyone know the schematic please help me soon.. i need to design myself.. wat are the components required..

thanks in advance

This is not meant to rain on your parade, but doesn't a design project imply attaining an understanding of the device sufficient to put the circuit together yourself? Perhaps we understand the term differently. The actual scanners are commercial devices and simply do not have construction details and circuitry published.

Unless you are very good with optics and can build a scanner, the capacitive type device might be easier to construct. That opinion is based on a one-liner from the Wikipedia article.

Practically speaking, purchasing a scanner and setting up the interface to let a microprocessor read it, as well as the programming might be as far as you would want to go.

I don't understand what type of capacitive sensor would give you an image of a fingerprint. Maybe a capacitive sensor could determine when an actual finger was placed on the scanner (as opposed to, say, just a fake image of a fingerprint).

Why can't you just use an imaging chip like those in digital cameras? You would probably need a lens system, so that the chip's image sensor surface could be far-enough away from the finger to get good focus, etc, and still have the fingertip fill the entire field of view (for best resolution).

In theory, with some microfabrication capability, one could make a matrix or a string of capacitive sensors which would have enough resolution to detect the individual dermal papillae.

BTW, here's an off-the-shelf fingerprint module: http://www.fingerprints.com/Products/Modules.aspx