Electro-optical filter

• US 7,755,720 B2
• Filed: 05/02/2006
• Issued: 07/13/2010
• Est. Priority Date: 05/10/2005
• Status: Expired due to Fees

• Current Assignee: Live Technologies, Ltd.
• Original Assignee: Live Technologies, Ltd.
• Inventors: Stephanov, Dmitri Yu, Butcher, Roland
• Primary Examiner(s): ROJAS, OMAR R
• Application Number:
  US11/913,770
• Publication Number:
  US 20080198279A1
• Time in Patent Office: 1,533 Days
• Field of Search: None
• US Class Current: 349/113
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/135 Liquid crystal cells structurally associated with a photoconducting or a ferro-electric layer, the properties of which can be optically or electrically varied G02F1/133348 takes precedence
• CPC Class Codes: H04N 23/75 by influencing optical camera components

Abstract

The present invention provides an electro-optical filter for filtering light from an object. The filter is arranged for receiving the light via a first imaging element and comprises a plurality of reflective elements for receiving and reflecting the light. Each reflective element has an optical property that is dependent on an intensity of the light at or near the reflective element. The optical property controls local filtering of the light intensity in a manner such that, above a predetermined intensity threshold, the filter reduces intensity differences of light originating from bright and dark regions of the object.

Claims

1. An electro-optical filter for filtering light from an object, the filter being arranged for receiving the light via a first imaging element and comprising:

a plurality of reflective elements for receiving and reflecting the light, each reflective element having an optical property;

control electronics comprising a plurality of optical elements and being positioned partially behind reflective surfaces of the reflective elements, each optical element being positioned at or near a respective reflective element for receiving the light form the same incident light pathway as the respective reflective element, each optical element being arranged to control the optical property of the respective reflective element as a function of an intensity of the received light; and

a beam splitter which is arranged for receiving light from the first imaging element and splitting the received light into light having two orthogonal polarisation states;

wherein the optical property controls local filtering of the light intensity in a manner such that, above a predetermined intensity threshold, the filter reduces intensity differences of light originating from bright and dark regions of the object.

2. The electro-optical filter as claimed in claim 1 wherein each reflective element is arranged so that a polarisation of the light is rotated as a function of light detected by the respective optical element.

3. The electro-optical filter as claimed in claim 1 comprising at least one matrix of the reflective elements.

4. The electro-optical filter as claimed in claim 1 comprising two matrices of the reflective elements.

5. The electro-optical filter as claimed in claim 1 wherein the optical elements are arranged to detect the local light intensity by exhibiting a respective electrical conductivity.

6. The electro-optical filter as claimed in claim 5 wherein each optical element is a photo-diode.

7. The electro-optical filter as claimed in claim 1 wherein each reflective element comprises a liquid crystal material.

8. The electro-optical filter as claimed in claim 7 wherein the liquid crystal material is positioned between a metallic reflective surface and a transparent conductive coating so that the metallic surface and the metallic coatings can be used to apply an electric field across the liquid crystal material.

9. The electro-optical filter as claimed in claim 3 wherein the or each matrix of reflective elements comprises a silicon substrate.

10. The electro-optical filter as claimed in claim 9 wherein the or each matrix of reflective elements is Liquid Crystal on Silicon (LCoS) device.

11. The electro-optical filter as claimed in claim 1, wherein the beam splitter comprises a birefringement beam splitter.

12. The electro-optical filter as claimed in claim 10 wherein each reflective element is arranged so that the light intensity detected by each photo-diode controls a voltage and the voltage controls the optical activity of a respective liquid crystal.

13. The electro-optical filter as claimed in claim 12 wherein each liquid crystal is arranged so that, above or below a threshold voltage applied to the liquid crystal, the liquid crystal effects a rotation of the polarisation of the reflected light by an angle between 0°

and 90°

.

14. The electro-optical filter as claimed claim 13 comprising a birefringent beam splitter and being arranged to direct substantially all reflected light having a polarisation rotated by 90°

so that it can be used for forming the image and for directing at least some of the light having a polarisation rotated by an angle smaller than 90°

so that it is not used for forming image.

15. The electro-optical filter as claimed in claim 1 wherein each reflecting element comprises electronic components that are embedded in a region underneath the reflective surface.

16. The electro-optical filter as claimed in claim 1 comprising at least one matrix of the reflecting elements and wherein the or each matrix of the reflective elements is an integrated device formed on a silicon substrate.

17. A viewing or image capturing device comprising:

an electro-optical filter for filtering light from an object, wherein the filter is arranged for receiving the light via a first imaging element, wherein the filter comprises

(i) a plurality of reflective elements for receiving and reflecting the light, each reflective element having an optical property, wherein the optical property controls local filtering of the light intensity in a manner such that, above a predetermined intensity threshold, the filter reduces intensity differences of light originating from bright and dark regions of the object;

(ii) control electronics comprising a plurality of optical elements and being positioned partially behind reflective surfaces of the reflective elements, each optical element being positioned at or near a respective reflective element for receiving the light form the same incident light pathway as the respective reflective element, each optical element being arranged to control the optical property of the respective reflective element as a function of an intensity of the received light; and

(iii) a beam splitter which is arranged for receiving light from the first imaging element and splitting the received light into light having two orthogonal polarisation states; and

a lens system configured to form an image from light having one of the Polarisation states.

18. A method of filtering light from an object, the method comprising:

receiving the light via a first imaging element by a plurality of reflective elements, each reflective element having a optical property that is dependent on an intensity of the light at or near the reflective element;

splitting the received light into light having two orthogonal polarisation states;

detecting the light intensity at or near each reflective element, the light being received for detection from the same direction as the light that is received by the reflective elements; and

controlling the optical property of each reflective element using control electronics positioned partially behind reflective surfaces of the reflective elements in a manner such that, above a predetermined light intensity threshold, the filter reduces intensity differences of light originating from bright and dark regions of the object.

19. An electro-optical filter for filtering light from an object, the filter being arranged for receiving the light via a first imaging element and comprising:

a plurality of reflective elements for receiving and reflecting the light, each reflective element having an optical property;

a plurality of optical elements, each optical element being positioned at or near a respective reflective element for receiving the light form the same incident light pathway as the respective reflective element, each optical element being arranged to control the optical property of the respective reflective element as a function of an intensity of the received light;

a birefringent beam splitter which is arranged for receiving light from the first imaging element and splitting the received light into light having two orthogonal polarisation states; and

wherein the optical property controls local filtering of the light intensity in a manner such that, above a predetermined intensity threshold, the filter reduces intensity differences of light originating from bright and dark regions of the object.

20. An electro-optical filter for filtering light from an object, the filter being arranged for receiving the light via a first imaging element and comprising:

a plurality of reflective elements for receiving and reflecting the light, each reflective element having an optical property comprising at least one matrix of the reflective elements comprising a silicon substrate wherein the or each matrix of reflective elements is Liquid Crystal on Silicon (LCoS) device, wherein each reflective element is arranged so that the light intensity detected by each photo-diode controls a voltage and the voltage controls the optical activity of a respective liquid crystal, and wherein each liquid crystal is arranged so that, above or below a threshold voltage applied to the liquid crystal, the liquid crystal effects a rotation of the polarisation of the reflected light by an angle between 0° and

90°

;

a plurality of optical elements, each optical element being positioned at or near a respective reflective element for receiving the light form the same incident light pathway as the respective reflective element, each optical element being arranged to control the optical property of the respective reflective element as a function of an intensity of the received light;

a birefringent beam splitter and being arranged to direct substantially all reflected light having a polarisation rotated by 90°

so that it can be used for forming the image and for directing at least some of the light having a polarisation rotated by an angle smaller than 90°

so that it is not used for forming image; and

wherein the optical property controls local filtering of the light intensity in a manner such that, above a predetermined intensity threshold, the filter reduces intensity differences of light originating from bright and dark regions of the object.