Browse Prior Art Database

Optical Path Length Equalizer

IP.com Disclosure Number: IPCOM000086502D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Thorp, LD: AUTHOR

Abstract

In dual-beam spectrophotometers, it is desirable to have equal path lengths for both the sample and reference beams to avoid any unbalanced operation. The drawing shows an optical path length equalizer 1 that can be inserted into one of the beams, the equalizer being adjustable to allow adjustments to be made in the path length.

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Optical Path Length Equalizer

In dual-beam spectrophotometers, it is desirable to have equal path lengths for both the sample and reference beams to avoid any unbalanced operation. The drawing shows an optical path length equalizer 1 that can be inserted into one of the beams, the equalizer being adjustable to allow adjustments to be made in the path length.

A first fiber-optic bundle 1 receives light for transmission. One end of the bundle has a D-shaped cross-section joined to a similarly shaped end of a semicylindrical glass rod 2. A similarly shaped but inverted glass rod 3 partially overlies or overlaps rod 2 and has its flat surface in contact with the flat surface of rod 2. The end of rod 3 is connected to a second fiber-optic bundle 4. Rods 2 and 3 are contained in a lucite sleeve 5. The rods and fiber-optic bundles are slidable longitudinally relative to each other to vary the amount of overlap between the rods to thereby vary the path length. This allows the path length to be adjusted. An index matching oil is applied to the adjacent surfaces of rods 2 and 3 to increase the transmission efficiency and decrease any interface interaction.

The equalizer has the advantage that the F number of light received by 1 remains the same as the F number of light emitted by bundle 4. In addition, by choosing rods 2 and 3 having a high index of refraction, no light leakage occurs into the lucite sheath 5.

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