Optical stethoscopy: Imaging with λ/20

Unprecedented optical image resolution has been obtained using a near-field optical scanner called "optical stethoscope": 20 to 30 nm with blue light of half a micron wavelength! Key element is an extremely small aperture (5-10 nm) placed at the very top of a sharply pointed pyramidal or conical screen. The aperture is scanned in the immediate proximity of the surface to be investigated. The amount of light transmitted by both aperture and sample depends sensitively on the optical properties of the sample in the immediate vicinity of the aperture. © 1986 SPIE.