Liquid crystal cells – elements and systems – Liquid crystal system – Liquid crystal eyewear
Patent
1997-07-17
1999-09-14
Sikes, William L.
Liquid crystal cells, elements and systems
Liquid crystal system
Liquid crystal eyewear
349 24, G02F 1136
Patent
active
059530820
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an electro-optical filter for an image capture or viewing device, and in particular, but not exclusively, to an electro-optical filter for modifying the contrast range of light emanating from a subject prior to capture or viewing of an image of that subject.
BACKGROUND OF THE INVENTION
There are many reasons why the ability to control the contrast characteristics of a subject image at the time of image capture is desirable, on both a technical as well as an aesthetic level. There has been many endeavours to control or modulate the contrast characteristics of a live subject image during image capture in a recording device. Liquid crystal filters have been described for modulating the subject image to reduce contrast and improve pick-up quality for example in JP 2-1832 (MATSUSHITA) and GB 2,255,465 (SONY). These patents describe multiplexed signal addressing of a filter matrix, and largely concentrate on the use of a beam splitting prism or partial mirror directing a sample subject image onto a separate sensor array to pick up a drive signal.
Although proposing an effective contrast modulating systems for a camera, the systems described in these prior art patents have several practical limitations. For example, the use of beam splitters or partial mirrors limits the amount of light which can reach a recording or viewing medium. Additionally, as it is only the portion of the light reflected by the prism or partial mirror which is acted upon by sensors, rather than the whole amount of available light, the overall system sensitivity and fidelity is reduced. A further disadvantage is the bulk, voltage requirement and overall expense of these systems.
As a result of the above disadvantages, to this day, systems such as those referred to above, do not appear to have gained commercial acceptance nor wide practical use.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electro-optical filter for filtering an image prior to capture or viewing which is small, compact and easy to manufacture at a low cost.
According to a first aspect of the present invention there is provided an electro optical filter adapted for location in an optical path between a subject and a focal plane for capture or viewing of an image of said subject, said filter comprising: image impinge, each cell having a transmissibility which varies in direct response to the intensity of the portion of subject image impinging on that cell, filtered by the cell on which it impinges so that a filtered subject image comprising the ensemble of said filtered subject image portions can be captured or viewed at said focal plane.
Preferably each cell comprises a body of liquid crystal material; and, a drive circuit for providing an electric field across said body of liquid crystal material to control the molecular alignment of said liquid crystal material, the strength of said electric field being directly dependant on the intensity of the portion of said subject image impinging on that cell.
Preferably said drive circuit includes a first component having an electrical characteristic which is variable in response to the intensity of the portion of said subject image impinging thereon for controlling the strength of said electric field.
Preferably said electrical characteristics is the impedance of said first component.
Preferably said drive circuit includes a second component connected with said first component to form a divider circuit wherein said electric field is generated from a point between said first and second components.
Preferably said second component is of fixed impedance.
Preferably said first component is made of a material having an impedance which varies in response to the intensity of electro magnetic radiation impinging thereon.
Preferably said material is configured in a convoluted path, or path of other configuration.
Preferably said divider circuit is a voltage divider circuit which divides a cell supply voltage between said first and second componen
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Parker Kenneth
Sikes William L.
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