fluid lenses

Today's words are "electrowetting" and "meniscus".

I thought I had posted about this a year or two ago, but if, so I can't find it now. Anyway, I think this article has more technical detail than whatever I read back then. This is really cool stuff: it means that there is some hope of having a small camera that can approach the quality of an SLR.

Through a Lens Sharply:

Our FluidFocus lens uses electrostatic forces to alter the shape of a drop of slightly salty water inside a glass cylinder 3 millimeters in diameter and 2.2 mm long. The lens exploits surface-tension characteristics of fluids.

The optical power of our lens, with its inner cylinder diameter of 3 mm, can vary over a range of 150 diopters. This is accomplished by changing the meniscus between hemispherical (its radius equal to half the diameter of the cylinder) and concave (its radius approximately equal to the diameter of the cylinder). If it were the same size as a human lens, its optical power range would be about 50 diopters -- 12 times as large as the optical power of the human eye, which has a range of about 4 diopters. [...]

We built a digital camera just 5.5 mm high and 4 mm across [...] By changing the voltage on the electrode of the liquid lens, we were able to focus on objects at distances anywhere from 2 centimeters up to infinity. [...]

Optical zooming requires at least two lenses -- one to change the magnification, the other to refocus the image. In principle, changing the magnification by moving the lens throws the image out of focus. Conventional cameras keep the image in focus through a system of rods that connect the separate lenses.

We are presently designing a zoom lens system that uses two liquid lenses in series. This lens will work by changing the shapes, and therefore the optical power, of the two lenses, rather than by changing their locations. Compared with conventional zoom lenses, liquid lenses will have two advantages: no moving parts and a very small size at, potentially, a very low cost.

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14 Responses:

  1. ralesk says:

    Photographers are totally going to e-wet themselves over this.

  2. rosefox says:

    Now I want to go off and amuse myself making up definitions for "mensicus".

  3. This fixes the zoom/focus issue, so that leaves light gathering issues, you still will need a larger-than-your-camera-phone's-pinhole-aperture worth of light for a good high res picture. Especially for you taking images in low light situations. But you should be able to get a thin depth with a lens sized width x height camera out of it.

    • jwz says:

      They say that the lenses have to be small, so that surface tension has more effect than gravity -- otherwise the lenses won't be symmetrical.

      But yeah, I did notice that while they talked about lens power, they didn't talk about brightness. I guess it depends on how transparent these oils are compared to a big hunk of glass.

      • treptoplax says:

        Even if it's 100% transparent, the killer is that a 2mm lens is only receiving (2^2)/(35^2) the light a 35mm lens does. CCDs are a lot more sensitive than film (which is why digital SLRs use smaller lenses than film cameras), but at some point you either give up resolution, or color depth, or speed, because there just aren't enough photons coming in.

        • vxo says:

          The difference, though, is that the CCD on a camera phone is really small. Proportionally, the lens fitted on camera phones is usually f/5.6 at the smallest and f/3.5 at the largest, roughly. (The f-stop ratio is basically the ratio of the area of the lens aperture to the area of the film or sensor; the largest lens I've used for 35mm film is f/1.4.)

          • treptoplax says:

            Well, yeah, that was what I meant; a small CCD means low resolution and/or long exposures and/or requiring very bright light. (I suppose making it B/W only would help, too...)

  4. aris1234 says:

    Here is more info from DPReview from some time back:


    I seem to recall some controversy about patents with this one.

  5. alisgray says:

    Frank Herbert talked about having fluid lenses in electrostatic fields for optics in the first Dune book. I wonder where he found the idea.

  6. kyronfive says:

    Here the looking glass of pride and ruined vanity.

  7. 5tephe says:

    But why are there only 150 diopters? Surely if you arranged it all to vary the voltage via an old school knob or dial, you could have an infinite set of focus stops?

    Or am I just being an Analogosaurous?