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Detector of Dichroic Absorption of Light

IP.com Disclosure Number: IPCOM000091102D
Original Publication Date: 1969-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Dreyfus, RW: AUTHOR

Abstract

A dichroic material is one which exhibits a different degree of optical absorption for light in two polarizations. Devices for measuring the dichroism of a material are dichroism spectroscopes. This dichroism spectroscope uses a single pulsed source of light 2 which produces beam 4 of unpolarized light. Dichroic crystal 6 lies in the path of beam 4 and absorbs horizontally polarized light differently than vertically polarized light. Wollaston prism 8 separates beam 4' transmitted through the sample into horizontally polarized beam 10 and vertically polarized beam 12. Both beams impinge on diode light detector 14. Beam 12 is delayed by its passage through light pipe 16.

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Detector of Dichroic Absorption of Light

A dichroic material is one which exhibits a different degree of optical absorption for light in two polarizations. Devices for measuring the dichroism of a material are dichroism spectroscopes. This dichroism spectroscope uses a single pulsed source of light 2 which produces beam 4 of unpolarized light. Dichroic crystal 6 lies in the path of beam 4 and absorbs horizontally polarized light differently than vertically polarized light. Wollaston prism 8 separates beam 4' transmitted through the sample into horizontally polarized beam 10 and vertically polarized beam 12. Both beams impinge on diode light detector 14. Beam 12 is delayed by its passage through light pipe 16.

As a result of the delay, assuming such a delay to result from a 60 cm. light pipe, electrical signals 11 and 18 are produced by detector 14 that are three nanoseconds apart. The amplitudes of pulses 17 and 18 are compared by electronic circuitry, not shown, to determine the difference, if any, in the amount of absorption by the material under test between the beam 10 and beam 12. If desired, a polarizer can be inserted between source 2 and sample 6 so that such polarizer, when rotated through the appropriate angle, absorbs more light of one polarized beam than the other polarized at right angles to it. The spectroscope is thus adjusted so that, with no dichroic sample present, the output pulses from the two differently polarized beams are of equal size.

Thi...