X-Message-Number: 3577 Date: Mon, 2 Jan 1995 13:52:55 -0800 From: John K Clark <> Subject: SCI.CRYONICS Finding small objects with light -----BEGIN PGP SIGNED MESSAGE----- Wrote: >Let me also remind them until recently scientist >thought is was impossible to resolve with light objects smaller >than the wave length of light. (Perry E. Metzger) Wrote: >To my knowldege, it is still impossible to do so >- -- STMs and AFMs don't use light. More than 100 years ago Ernst Abbe proved that details smaller than half the wavelength of the light used to illuminate a specimen could not be resolved, but he made a hidden assumption, namely that the distance between the specimen and the source of light was large compared to the wavelength. In 1956 J.A. O'Keefe proposed a "scanning near field microscope" that would break the Abbe barrier. O'Keefe said that if light was emitted from a tiny hole less than a wavelength away from the specimen the resolution would be limited only by the size of the hole, the wavelength would be irrelevant. In 1972 Eric Ash proved experimentally that O'Keefe was correct. It looks like this technique may soon be practical. In 1993 Eric Betzig of ATT used visible light from a laser 10 nanometers above a sample to reveal details of the skeletal scaffolding inside a cell as small as 15 nanometers. Visible light is about 500 nm. John K Clark -----BEGIN PGP SIGNATURE----- Version: 2.6.i iQCzAgUBLwhx/X03wfSpid95AQE7YwTwyf9PN60RDVhvit05m1zAW9pu6YOhoEsH +3bQBC6bhwimhgvQzitF2gyu65CueUhT62MsikR2Pp89tJ8YRFPYC+jU+IVoWO+v QXpHUwJTm29XwJNhL+hScXb9DkpPurk15Q7OpVdqFdkRGgzjB2efSG9ADKBSBZMG s4iiNaQ6DYEm/Qm4UjDa+QQDiej2L17dDO/nR2bATJejywi3ruU= =LZnr -----END PGP SIGNATURE----- Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=3577