TUNABLE LIQUID LENS WITH REDUCED ABERRATION
First Claim
1. An imaging device comprising:
- an image sensor;
a fixed lens assembly having a mounting for said image sensor at which a far field is in focus on said image sensor;
a tunable liquid crystal lens mounted in an optical path of said image sensor and said fixed lens assembly, said tunable liquid crystal lens having an optical power that increases from zero field level to a maximum power at a second field level, and decreases from said second field level to a non-zero end optical power at a desired maximum field level; and
an optical power adjustment element comprising at least one of a spacer and an additional lens, wherein said optical power adjustment element cancels said non-zero optical power so that said image sensor receives a far field image at said desired maximum field level.
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Accused Products
Abstract
A tunable optical imaging system uses a fixed lens and a tunable liquid crystal lens that is operated only outside of an operational range of high aberration. A voltage range applied to change the optical power of the liquid crystal lens is limited to a continuous tunable range of low aberration. The relative positioning between the lens and a corresponding photodetector, and the relative lens powers of a fixed lens and the tunable lens, may be selected to compensate for any optical power offsets resulting from the limitation of the voltage range of the tunable lens. The lens may be operated in either positive tunability or negative tunability mode.
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Citations
24 Claims
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1. An imaging device comprising:
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an image sensor; a fixed lens assembly having a mounting for said image sensor at which a far field is in focus on said image sensor; a tunable liquid crystal lens mounted in an optical path of said image sensor and said fixed lens assembly, said tunable liquid crystal lens having an optical power that increases from zero field level to a maximum power at a second field level, and decreases from said second field level to a non-zero end optical power at a desired maximum field level; and an optical power adjustment element comprising at least one of a spacer and an additional lens, wherein said optical power adjustment element cancels said non-zero optical power so that said image sensor receives a far field image at said desired maximum field level. - View Dependent Claims (2, 3, 4, 5, 6, 13)
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7. An imaging device comprising:
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an image sensor; a liquid crystal layer; an electric field source providing a variable, spatially non-uniform electric field across the liquid crystal layer to provide a tunable range of optical power, wherein said layer, under the effect of said electric field, forms a tunable liquid crystal lens having a variable optical power that changes in a first direction with an increase in the strength of the electric field from an initial optical power to a peak optical power, and which changes in a second direction with a further increase of the strength of the electric field from said peak optical power to a non-zero end optical power different from the initial optical power, and wherein operation of the liquid crystal layer is limited to a continuous, non-zero tunable operational optical power range between the peak optical power and the end optical power; and one or more fixed lenses cooperating with said liquid crystal lens at non-zero optical power to focus an image onto said image sensor with an infinity focus near one limit of said tunable range. - View Dependent Claims (8, 9, 10, 11, 12)
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14. A method of controlling a tunable optical device having a liquid crystal layer and a variable, spatially non-uniform electric field applied across the liquid crystal layer to provide a tunable range of an optical property, the method comprising:
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detecting at least one of aberration and scattering caused by said liquid crystal layer under conditions of relatively low electric fields and determining a corresponding optical quality of said device as a function of electric field; determining a preferred range of operation for said electric field that avoids a range at which said optical quality is less desirable; and generating said electric field in accordance with a desired optical value for said device within said preferred range of operation. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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- 21. A tunable optical device having a liquid crystal layer and a variable, spatially non-uniform electric field applied across the liquid crystal layer to provide a tunable range of an optical property, said device having an electric field controller setting an electric field control signal in response to a desired optical value signal, said electric field controller having an offset value restricting a range of operation of said tunable range to reduce an effect of at least one of aberration and scattering caused by said liquid crystal layer under conditions of relatively low electric fields.
Specification