Tunable electro-optic filter stack

Patent metadata

Field	Value
Publication number	US-9752932-B2
Application number	US-201113881608-A
Country	US
Kind code	B2
Filing date	Oct 29, 2011
Priority date	Mar 10, 2010
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

A holographic polymer dispersed liquid crystal (HPDLC) tunable filter exhibits switching times of no more than 20 microseconds. The HPDLC tunable filter can be utilized in a variety of applications. An HPDLC tunable filter stack can be utilized in a hyperspectral imaging system capable of spectrally multiplexing hyperspectral imaging data acquired while the hyperspectral imaging system is airborne. HPDLC tunable filter stacks can be utilized in high speed switchable optical shielding systems, for example as a coating for a visor or an aircraft canopy. These HPDLC tunable filter stacks can be fabricated using a spin coating apparatus and associated fabrication methods.

First claim

What is claimed:

1. A hyperspectral imaging system comprising:
a hyperspectral imager that includes a holographic polymer dispersed liquid crystal (HPDLC) tunable optical filter through which light passes, the hyperspectral imager configured to acquire and spectrally multiplex hyperspectral imaging data, wherein:
the HPDLC tunable optical filter comprises a stacked assembly of two or more HPDLC thin film elements, each HPDLC thin film element being switchable between a light reflecting state and a transparent or semitransparent state with a switching time of no more than twenty microseconds; and
each HPDLC thin film element, when in its light reflecting state, reflects a different Bragg wavelength than the other HPDLC thin film elements such that when exposed to incident light and in its respective reflecting state, each HPDLC thin film element allows a different spectrum of incident light to be transmitted through the stack,
the collective sets of spectra of incident light from the plurality of HPDLC thin film elements being the hyperspectral imaging data.

2. The hyperspectral imaging system of claim 1 , wherein a first holographic polymer dispersed liquid crystal thin film of the plurality abuts a first surface of an intervening conductive layer and a second holographic polymer dispersed liquid crystal thin film of the plurality abuts an opposed second surface of the intervening conductive layer.

3. The hyperspectral imaging system of claim 1 , wherein each of the plurality of holographic polymer dispersed liquid crystal thin films abuts a surface of a conductive element disposed adjacent to the holographic polymer dispersed liquid crystal thin film element.

4. The hyperspectral imaging system of claim 1 , wherein the holographic polymer dispersed liquid crystal tunable filter comprises a stack of alternating holographic polymer dispersed liquid crystal thin film elements and conductive elements.

5. The hyperspectral imaging system of claim 4 , wherein the conductive elements comprise respective discrete layers of PEDOT:PSS.

6. The hyperspectral imaging system of claim 1 , wherein each of the holographic polymer dispersed liquid crystal thin film elements comprises a film thickness of no more than twenty microns.

7. The hyperspectral imaging system of claim 1 , wherein the holographic polymer dispersed liquid crystal tunable filter is capable of facilitating the acquisition of hyperspectral imaging data throughout a wavelength range of approximately 780 nm to approximately 3 μm.

8. The hyperspectral imaging system of claim 1 , further comprising a transmitter configured to transmit the acquired hyperspectral imaging data.

9. The hyperspectral imaging system of claim 1 , further comprising a platform configured to carry the hyperspectral imager, the platform configured to facilitate airborne collection of the hyperspectral imaging data.

10. The operating hyperspectral imaging system of claim 1 , wherein each HPDLC thin film element is individually biased between its respective light reflecting and transparent or semitransparent states.

11. The hyperspectral imaging system of claim 1 , wherein each HPDLC thin film element, when in its light reflecting state, reflects a different Bragg wavelength with a resolution of less than 10nm.

12. The hyperspectral imaging system of claim 1 , wherein the reflection wavelength of each HPDLC thin film element has a full width at half maximum (FWHM) in a range of from 5 to 20nm.

13. An operating hyperspectral imaging system comprising:
a hyperspectral imager that includes a holographic polymer dispersed liquid crystal (HPDLC) tunable filter, the hyperspectral imager acquiring and spectrally multiplexing hyperspectral imaging data from the tunable filter, wherein:
the HPDLC tunable filter comprises a stacked assembly of two or more HPDLC thin film elements, each HPDLC thin film element being switched during operation between a light reflecting state and a transparent or semitransparent state with a switching time of no more than twenty microseconds;
each HPDLC thin film element is designed to reflect a different Bragg wavelength across an operating bandwidth; and
when exposed to incident light and in its respective light reflecting state, each HPDLC thin film element is generating a unique set of spectral data,
the collective sets of spectral data from the plurality of HPDLC thin film elements being the hyperspectral imaging data.

14. The operating hyperspectral imaging system of claim 13 , wherein the holographic polymer dispersed liquid crystal tunable filter comprises a stack of alternating holographic polymer dispersed liquid crystal thin film elements and conductive elements.

15. The operating hyperspectral imaging system of claim 13 , wherein each HPDLC thin film element, when in its light reflecting state, is reflecting a different Bragg wavelength with a resolution of less than 10nm.

16. The operating hyperspectral imaging system of claim 13 , wherein each HPDLC thin film element is individually biased between its respective light reflecting and transparent or semitransparent states.

17. The operating hyperspectral imaging system of claim 13 , further comprising a transmitter that is transmitting the acquired hyperspectral imaging data.

Assignees

• Fontecchio Adam K
• Shriyan Sameet K
• Bellingham Alyssa
• Univ Drexel

Inventors

• Fontecchio Adam K
• Shriyan Sameet K
• Bellingham Alyssa

Classifications

• G01J3/502

  using a dispersive element, e.g. grating, prism · CPC title

• G02F1/13476

  in which at least one liquid crystal cell or layer assumes a scattering state · CPC title

• G01J3/51

  using colour filters · CPC title

• G01J3/0237 Primary

  Adjustable, e.g. focussing · CPC title

• G02B27/0103

  comprising holographic elements · CPC title