Question about how touchscreens work

[gtglew]

Hello All,

This is my first post on the forum. I registered today after spending some time searching for my answer. My company develops Biometric software which uses many metrics the iPhone/iPod/iPad touch to assess the identity of the user.

My task has been to try and find out if the touchscreen on these devices is sensitive enough to get any kind of fingerprint. Our software can accurately identify a fingerprint with only a partial print at 160dpi. After much searching and discussion, I am still at a loss. I have a few questions and was hopeful someone here could help answer.

1. How does the screen respond to a touch on the screen? Does it sense the capacitance difference between the valley/ridges of a finger print?

2. When I was reviewing capacitance fingerprint scanners, it appears to be the same technology. After a few conversations with touchscreen manufacturers, it seems the technology is very similar but a phone touchscreen has much fewer electrodes and uses interpolation and different to determine where on the screen is being pressed.

I know these are broad questions, but I'm having a difficult time even trying to figure out the right questions to ask. The basic question I have is:

Does a iDevice have enough sensitivity in the screen to pull a rough fingerprint image? If not, why not?

Any help would be greatly appreciated.

 

[TJ61]

Capacitive touchscreens are not measuring capacitance between two different parts of your finger, but rather a change in capacitance of screen elements when your finger touches the screen (and disturbs the electrostatic field in that region). So, there's really no chance of any "imaging", and certainly not at the resolution you're looking for.

Regards,
Tom

 

[gtglew]

Capacitive touchscreens are not measuring capacitance between two different parts of your finger, but rather a change in capacitance of screen elements when your finger touches the screen (and disturbs the electrostatic field in that region). So, there's really no chance of any "imaging", and certainly not at the resolution you're looking for.

Regards,
Tom

Great info...

search term: raw touchscreen data pulled up some interesting stuff and was very useful for me.

I've been focusing on iDevices but it seems like Android may offer more access to this raw data. I'm inching toward the conclusion that the device is simply passing off X,Y coordinates to the software, I'd like to find some proof of this. Maybe I need to find out how a capacitance fingerprint scanner works to determine how much different it is than a capacitance touchscreen.

 

[Ramonn]

+1

Whatever you find and what ever you do, please share it.

Thank you.