Image courtesy Authentec
In the last look at Authentec, Apple’s integration of a fingerprint sensor into their design strategy was presented as central. Namely, it does not seem very “Apple” to have a stand-alone extra “thing”. Certainly one approach to this end would be the integration of any sensor into existing features/surfaces. One could envision a roadmap for incorporating a capacitance sensor into existing touch surfaces. There is also the possibility that another sensor technology peeked Apple’s interest. A technology that might be more seamlessly integrated into their devices. One technology that has come to light is Authentec’s RF imaging technology. Apple loves wireless and it may just be a technology that can provide a more seamless integration. In particular this slide deck on AuthenTec’s TruePrintTM reared its head. Time to take a look.
Basics of RF imaging technology are presented, for example, in Slide 2 of the above-mentioned slide deck. An AC signal generator is connected between two conductive plates, forming an electric field therebetween. If one of these plates is corrugated this shape will be imparted on the field. In this application the conductive, corrugated plate is a finger. Now with the placement of an antenna array between the plates one can detect the ridges and valleys of the fingers. As long as one makes electrical contact with the finger this seems like a neat means of imaging a fingerprint.
A bit more poking around finds US patent 5,940,526 (‘526) describing an electric field fingerprint sensor. In passing it was interesting to note the ‘526 patent was first assigned to Harris Corporation (I knew Melbourne, Florida sounded familiar).
There is still an integration issue as one needs to make electrical contact with the finger while maintaing RF transparency. Both the slide deck and the ‘526 disclose a conductive ring around the RF transparent surface. This again does not seem very Apple. These extra two rings would likely be rejected by the product designers. But, I am going to throw one more thing in the mix, Liquidmetal. While they have been in a licensing relationship, now extended, since 2010 there have not been any meaning products as yet. Of interest here are the persistent rumours that Liquidmetal is RF transparent. At this point this particular feature is not easily confirmed and I have not spent cycles thinking about the first principles. That said this would be one more feature that could make RF transparency relatively difficult to verify through public sources.
There is however still one thing that jumps out in all this - the dates. The ‘526 patent was filed in 1997 and the slide deck has a June 2002 date associated with it. This is not new technology, suggesting there may still be some piece of the puzzle holding back its adoption, a piece that may have just been solved.