US 5,159,486 AGranted

Instrumentation apparatus and methods utilizing photoconductors as light-modulated dielectrics

AssigneeInnova Laboratories, Inc.

InventorGeorge W. Webb

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Abstract

A light-modulated photoconductor, exhibiting a variable permittivity, provides the basis for various instrumentation devices and methods. In one embodiment, the light-modulated photocondcutor is used as a dielectric between conductive plates to provide a light-modulated capacitor (photocapacitor). One of the conductive plates may be transparent to facilitate application of the modulating light to the photoconductor. The light-modulated capacitor may be used for numerous applications, such as instrumentation used to, e.g., measure the work function of surfaces during processing or as a non-contact voltmeter. In another embodiment, the light-modulated photoconductor is used as a mirror or lens wherein the index of refraction is optically modulated. Such light modulated lens or mirror assembly may be used as a beam steering device, e.g., a solid state infra-red (IR) beam steering device.

Claims11

Dependent claims

Beam steering apparatus comprising:

a photoconductor having a band gap frequency, said photoconductor exhibiting a first permittivity when not exposed to light or when exposed to light of frequencies less than said band gap frequency, and a permittivity other than aid first permittivity when exposed to light of frequencies greater than said band gap frequency, said photoconductor being transparent to a beam of electromagnetic radiation of a frequency less than said band gap frequency, said transparent photoconductor exhibiting an index of refraction that varies as a function of the permittivity exhibited by said photoconductor;
light exposing means for selectively exposing said photoconductor to light having frequencies greater than said band gap frequency, whereby said photoconductor exhibits a permittivity other than said first permittivity when so exposed, said light exposing means further including means for exposing said photoconductor to light having an intensity profile that varies in tow directions, said light causing a volume to be created within said photoconductor that exhibits different permittivities than said first permittivity;
and
beam directing means for directing a beam of electromagnetic radiation toward said photoconductor, the amount of refraction or bending of said beam as it passes through said volume of said photoconductor being controlled by selectively exposing said photoconductor to light with said light exposing means.

1 more element

A method of optically steering an electromagnetic beam, said method comprising the steps of:

(a) directing said electromagnetic beam through a photoconductor substantially transparent to said electromagnetic beam said photoconductor having a band gap frequency, said electromagnetic beam having a frequency less than said band gap frequency, said photoconductor exhibiting a first permittivity when not exposed to light or when exposed to light of frequencies less than said band gap frequency, and a permittivity other than said first permittivity when exposed to light of frequencies greater than aid band gap frequency, said photoconductor further exhibiting an index of refraction that varies as a function of the permittivity of said photoconductor;
and
(b) optically changing the index of refraction of said photoconductor by selectively exposing said photoconductor to light having frequencies greater than said band gap frequency, said light having an intensity profile that varies in two directions, said light causing a volume to be created within said photoconductor that exhibits different permittivities than said first permittivity when so exposed, thereby altering the index of refraction of said photoconductor within said volume, thereby altering the amount said electromagnetic beam is refracted as it passes through said volume of said photoconductor.

Dependencies are inferred from the claim text.