Browse Prior Art Database

Optical Attenuator

IP.com Disclosure Number: IPCOM000086501D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Chiaramonte, R: AUTHOR [+4]

Abstract

All materials exhibit nonuniform energy absorption as a function of wavelength. As a consequence, any neutral density filter used to attenuate light levels causes unequal percentages in the transmitted energy. To minimize the optical variations, different materials are deposited as absorbing or reflecting layers on some type of substrate for transmission and reflective filters. This becomes expensive and complex because the optical properties or spectral responses must each be compensated for. In addition, none of these techniques provides an attenuator which is usable across the ultraviolet, visible and near-infrared range.

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Optical Attenuator

All materials exhibit nonuniform energy absorption as a function of wavelength. As a consequence, any neutral density filter used to attenuate light levels causes unequal percentages in the transmitted energy. To minimize the optical variations, different materials are deposited as absorbing or reflecting layers on some type of substrate for transmission and reflective filters. This becomes expensive and complex because the optical properties or spectral responses must each be compensated for. In addition, none of these techniques provides an attenuator which is usable across the ultraviolet, visible and near- infrared range.

The drawing shows an optical attenuator 1 having a series of different-sized pinhole attenuators 2 mounted on an indexable rotary wheel 3. The wheel is connected to and driven by a stepping motor 4. Light from a source 5 is directed by a condenser lens 6 to a slug 7 formed of a fiber-optic bundle. Light emerging from slug 7 is directed to the aligned pinhole attenuator 2. The slug 7 decomposes the incidence F cone into an array of cones each having the same F number as the incidence beam. Attenuator 2 attenuates the emerging beam through vignetting and allowing only the central part to pass, dependent upon the size of the pinhole therein.

The use of different pinhole sizes, without the use of a fiber-optic slug, is disadvantageous because the system or instrument response would be modulated nonlinearly (i.e., diffraction a...