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Noise Suppression in Standing Wave Memory Readout

IP.com Disclosure Number: IPCOM000093303D
Original Publication Date: 1967-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Sincerbox, GT: AUTHOR

Abstract

In the process of reading out information from a standing wave memory, interference occurs in the reflected light waves. This is due to the thin-film nature of the recording media. This interference is manifested as noise in the detected signals. The noise causes a serious loss in the signal-to-noise ratio and distortion of the signal shape. As the Fourier spectrum of the noise is sufficiently different from that of the information, this system spatially separates this noise from the information signals.

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Noise Suppression in Standing Wave Memory Readout

In the process of reading out information from a standing wave memory, interference occurs in the reflected light waves. This is due to the thin-film nature of the recording media. This interference is manifested as noise in the detected signals. The noise causes a serious loss in the signal-to-noise ratio and distortion of the signal shape. As the Fourier spectrum of the noise is sufficiently different from that of the information, this system spatially separates this noise from the information signals.

Readout signal 1, containing both noise and information from a selected position of the standing wave memory, is supplied to the system. It is displayed in a plane by dispersing the light beam with transmission grating 2 formed of alternate light and dark bars. The spectral content of the input signal containing both information and noise is indicated at 3. For the noise this appears as alternate light and dark bars that change in wavelength from one side to the other with increasing spacing as the wavelength of the light increases. The information also appears as bars that change in wavelength but with a constant separation.

A Fourier transformation is made of the spectral content of the input signal by positioning a lens set including lenses 4 and 5 in the path or the beam. Lenses 4 and 5 are separated by their focal length f. To remove the noise from the input signal, plate 6 having a number of aperture stops 7...