Re: barrier penetration, evanescent waves

[Brian Whatcott <betwys@DIRECTVINTERNET.COM>]

My guess:
the seminar appears to be set up to demonstrate that if the illumination can be
monotonic, then a holographic replica can do the work of a glass optical 
element.

This approach can be helpful where space is at a premium, or quantities of 
optics are needed at attractive prices.

Brian

At 08:36 PM 9/16/02, you wrote:
> Coincidence:
>
> Thursday September 19 @ 04.pm SCI 242
> * Physics Seminar * Fall 2002 *
>
> Professor Ramen Bahuguna
> Physics Department
> San Jose State University
>
> A Holographic Fingerprint Sensor
>
> A prism fingerprint sensor based on total internal reflection has an inherent
>
> problem:  the image is aberrated and distorted.  The main reason is that the
> image is inclined to the camera and expensive optics is needed to correct the
>
> aberrations.
> A simple holographic optical element (a holographic diffraction grating) can
> correct the above problems.  A fingerprint sensor incorporating such a
> grating will be demonstrated.
>
>
> For more information, or to get on the Physics Seminar e>mail list,
> or to enroll in Phys285 (till 9/20)
> please contact Carel Boekema, Seminar Coordinator.
> c•boekema  4 - 5260 boekemac@aol.com
> Office Hours MWF 9.30 - 10.20 and MW 11.30 - 12.20 Sci 303
>
>
>
>
> Bernard Cleyet wrote:
>
> > "... But a finger has
> > just the right combination of compliance and texture
> > so that the ridges of the fingerprint absorb the
> > evanescent wave (while the intervening valleys don't),
> > resulting in a very-high-contrast image of the fingerprint."
> >
> > I forgot to mention that this is the method for fingerprinting (a digital
> > camera views the ftir image and sends it to the DOJ)
> >
> > Before I do my demo. (semi-quantitative) for the HS Physics class, the
> > instructor has passed out glass prisms for the students to see for
> > themselves.
> >
> > bc who was finger printed this way as a requirement for a teaching
> > credential.
> >
> > "John S. Denker" wrote:
> >
> > > Bernard Cleyet wrote:
> > > >
> > > > A model for barrier penetration is FTIR (frustrated total internal
> > > > reflection).  The model is exact in that the equations are of the same
> > > > form (obvious, they're both described by the same wave equation).
> > >
> > > Yup.
>
> cut

Brian Whatcott
  Altus OK                      Eureka!