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Digital Indexed Angular Light Deflection System

IP.com Disclosure Number: IPCOM000096734D
Original Publication Date: 1963-Oct-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 3 page(s) / 42K

Publishing Venue

IBM

Related People

Fleisher, H: AUTHOR [+3]

Abstract

A light beam is positioned by a digital indexing technique. There are two critical angles of total internal reflection that exist for an optical birefringent crystal. These angles are related to the birefringent crystal's two indexes of refraction, the ordinary and the extraordinary indexes. An electro-optic active crystal positioned in front of a birefringent crystal controls the direction of light polarization entering the birefringent crystal.

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Digital Indexed Angular Light Deflection System

A light beam is positioned by a digital indexing technique. There are two critical angles of total internal reflection that exist for an optical birefringent crystal. These angles are related to the birefringent crystal's two indexes of refraction, the ordinary and the extraordinary indexes. An electro-optic active crystal positioned in front of a birefringent crystal controls the direction of light polarization entering the birefringent crystal.

A first light beam having a certain direction of polarization enters the birefringent crystal so that it strikes the exit surface at the critical angle for the higher index of refraction. It is totally reflected at the same angle back through the birefringent crystal. A second light beam having a polarization direction differing by 90 degrees from the first beam enters the birefringent crystal. The second beam has a larger critical angle, due to its difference in polarization direction, so it will pass through the exit surface into the adjacent medium where it strikes a mirror.

To avoid partial reflection and refraction of the second beam at the boundary surface, the medium between the birefringent material and the mirror has the same index of refraction as the smaller one of the indexes of refraction of the birefringent material. This intermediate medium can be a birefringent material. The arrangement of a series of alternate electro-optic and birefringent crystals together with associated mirrors allows the digital positioning of an entering light beam. The associated mirrors can be tilted a like amount to give an angular displacement in addition to the linear displacement of the light beam.

In this linear light deflection system, light from light source 10 is passed through collimating lens 12, linear light polarizer means 14, and aperture 18 in plate 16. The portion of the light beam passing through aperture 18 is directed normal to and through crystal 19. The light beam passes from crystal 19 to electro-optic controllable devices 20. This includes electro-optic crystal 24 and a pair of transparent electrodes 26 on opposite sides of the crystal 24. T...