Browse Prior Art Database

VARIABLE NEUTRAL DENSITY DEVICE

IP.com Disclosure Number: IPCOM000023025D
Original Publication Date: 1976-Jun-30
Included in the Prior Art Database: 2004-Mar-27
Document File: 2 page(s) / 391K

Publishing Venue

Xerox Disclosure Journal

Abstract

Cascaded, partially twisted nematic elements are provided between crossed polarizers to provide a variable neutral density device, Each of the partially twisted nematic elements comprises a twisted nematic sandwiched between two electrodes,

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Page 1 of 2

XEROX DISCLOSURE JOURNAL

VARIABLE NEUTRAL DENSITY Proposed Classification
DEVICE U.S. Cl, 350/16OLC
Gary A, Dir mt. Cl, G02b 5/23

POLARIZER POLARIZER

~NCOM~NG

LJGHT

FIG. 1

Volume 1 Number 6 june 1976 79

[~

            2NESA GLASS
TWISTED
NEMAT~C

F1&~2

Cascaded, partially twisted nematic elements are provided
between crossed polarizers to provide a variable neutral
density device, Each of the partially twisted nematic
elements comprises a twisted nematic sandwiched between two
electrodes,

Incoming light is rotated (90/n)° for n number of elements
in between the crossed polarizers, For example, if three
elements are used, and with no electrical field applied, the
first element 1 rotates the plane of polarization A of light
by 30° to B, the second element 2 imparts another 30° of
rotation for a total of 60° to C and the third element 3
imparts yet a further 30° rotation to the light for a total
of 90° of rotation to D, If any one element is electrically
activated, all successive elements must also be activated to
assure the retention of linearly polarized light at all
points along the optical path allowing the device to perform
without color dispersion and behave in a truly neutral
fashion, Each electrically activated element assumes the
homeotropic state and does not therefore alter the state of
polarization of normally incident light, Thus, the amount

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Page 2 of 2

VARIABLE NEUTRAL DENSITY DEVICE (Cont~d)

of rotation desired to be imparted to light can be selec-
tively controlled,

If the device is placed at the aperture stop of a lens, it
behaves as an electro~-optical shutter of variable transmit-
tance, It can also func...