Optical: systems and elements – Optical modulator – Light wave temporal modulation
Patent
1995-10-03
1998-01-27
Ben, Loha
Optical: systems and elements
Optical modulator
Light wave temporal modulation
359256, 359483, 359494, 359558, 351158, 351 41, 351 44, 351168, G02F 103, G02C 100
Patent
active
057127212
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a lens whose properties are variable.
The present invention has particular applicability in the area of bifocal lenses, and especially those used in ophthalmic applications, particularly contact lenses or intra-ocular lenses. Traditionally, contact and intra-ocular lenses have used a number of different techniques to allow users to see both near and distant objects. These techniques can be summarized as: each eye, one for near and one for distance vision. images focused on the retina simultaneously and the brain learns to distinguish the images and ignore the unwanted one; this may be achieved by the use of area division of the lens, polarization division, chromatic division, or bifocal diffractive lenses. the lens correctly in the eye. The lens moves up and down across the cornea depending on whether the eye looks up or down. When looking down, the user sees through a different optical power.
All of these techniques have particular disadvantages. The first two share the common disadvantage that the user is continuously confronted with two images. In many situations, this compromises the quality of vision. A particular example is that of driving at night, when the user sees both focused and blurred oncoming headlamps simultaneously which leads to an inability to see the road ahead clearly. Translating bifocals are based on the assumption that, when looking straight ahead, the user needs only distance vision and that, when looking down, the user needs only near vision. This is not always the case and is disadvantageous in many circumstances.
This invention aims to overcome these problems by providing a lens which can be switched between near and distance vision by the user. In the case of contact or intra-ocular lenses, the lens can be switched by the wearer; the user is therefore given the flexibility of a bifocal lens with the visual acuity of a monofocal lens.
The invention also has application in broader areas of optics. For example, it can provide a lens of variable focal length for use in compact disc players or optical memory disc drives.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a lens assembly comprising: electric or magnetic field, said property being at least one of the focal length, absorption, colour, and effective aperture; lens; and,
The power source may be a conventional miniature battery or a photocell, for example. In this latter case, the unit has no power source other than the light incident upon it. In its primary intended application as an ophthalmic lens, the power source may be a battery operable using the tear fluid for its activation.
In one preferred embodiment where the lens is used as an ophthalmic lens, the user can control the lens assembly by a deliberate (voluntary) eye action that is distinct from usual normal eye actions. An example of this is an extended blink. A normal involuntary blink lasts around 1/10 sec. A deliberate, longer blink (conveniently not so long as to look unnatural) could provide a trigger for the lens to change focal length. For implementations employing a photocell as power source, in very dark conditions, when the device is powered only to a very low level by the incident illumination, it can for example conveniently revert to a focal length which will provide distance vision.
It should be noted that the word "switch" is used in the following text primarily to refer to a change from one of two binary imaging states to the other. However, it should be read also to include an analogue change intermediate between those binary states. Such analogue switching could be useful in some applications (e.g. technical optics) where variable focal length, colour or aperture are desirable. For example, a variable focal length lens would have application in focus servo systems used in compact disc players.
The present invention is described in detail below only with reference to ophthalmic applications, although other applications should be understood.
BRIEF DESCR
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Ben Loha
Technology Partnership PLC
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