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Philips Develops Fluid Lenses
Lars T. writes "Digital Photography Review has a short report indicating: 'Philips Research at the CeBIT exhibition is demonstrating a unique variable-focus lens system that has no mechanical moving parts. Suited to a wide range of optical imaging applications, including digital cameras.' Here is Philips' press release and the Heise News article (in German) where I first heard about it. The latter also mentions that Philips has recently used the same electrowetting effect in an 'ePaper' display prototype."
There was an article in New Scientist a few weeks ago about a lense that changed it's focus in response to an electric current, iirc.
It was made of some plastic and I think the current changed the density of the plastic at some point in the structure in order to change the focus.
Of course, the aim was the same: "Make a lense without moving parts" - these guys must have developed a better solution because the Lense was very poor in the NS article.
Simon.
Philips' Fluid Lenses
Wednesday, 3 March 2004 21:40 GMT
Philips Research at the CeBIT exhibition is demonstrating a unique variable-focus lens system that has no mechanical moving parts. Suited to a wide range of optical imaging applications, including digital cameras. Philips' FluidFocus system mimics the action of the human eye using a fluid lens that alters its focal length by changing its shape. The new lens, which lends itself to high volume manufacturing, overcomes the fixed-focus disadvantages of many of today's low-cost imaging systems.
Press Release:
Philips' Fluid Lenses Bring Things into Focus
At this year's CeBIT Exhibition in Hannover Germany, Philips Research is demonstrating a unique variable-focus lens system that has no mechanical moving parts. Suited to a wide range of optical imaging applications, including such things as digital cameras, camera phones, endoscopes, home security systems and optical storage drives, Philips' FluidFocus system mimics the action of the human eye using a fluid lens that alters its focal length by changing its shape. The new lens, which lends itself to high volume manufacturing, overcomes the fixed-focus disadvantages of many of today's low-cost imaging systems.
The Philips FluidFocus lens consists of two immiscible (non-mixing) fluids of different refractive index (optical properties), one an electrically conducting aqueous solution and the other an electrically non-conducting oil, contained in a short tube with transparent end caps. The internal surfaces of the tube wall and one of its end caps are coated with a hydrophobic (water-repellent) coating that causes the aqueous solution to form itself into a hemispherical mass at the opposite end of the tube, where it acts as a spherically curved lens.
The shape of the lens is adjusted by applying an electric field across the hydrophobic coating such that it becomes less hydrophobic - a process called 'electrowetting' that results from an electrically induced change in surface-tension. As a result of this change in surface-tension the aqueous solution begins to wet the sidewalls of the tube, altering the radius of curvature of the meniscus between the two fluids and hence the focal length of the lens. By increasing the applied electric field the surface of the initially convex lens can be made completely flat (no lens effect) or even concave. As a result it is possible to implement lenses that transition smoothly from being convergent to divergent and back again.
In the FluidFocus technology demonstrator being exhibited by Philips Research at CeBIT 2004, the fluid lens measures a mere 3 mm in diameter by 2.2 mm in length, making it easy to incorporate into miniature optical pathways. The focal range provided by the demonstrator extends from 5 cm to infinity and it is extremely fast: switching over the full focal range is obtained in less than 10 ms. Controlled by a dc voltage and presenting a capacitive load, the lens consumes virtually zero power, which for battery powered portable applications gives it a real advantage. The durability of the lens is also very high, Philips having already tested the lens with over 1 million focusing operations without loss of optical performance. It also has the potential to be both shock resistant and capable of operating over a wide temperature range, suiting it for mobile applications. Its construction is regarded as compatible with high-volume manufacturing techniques.
(A) Schematic cross section of the FluidFocus lens principle. (B) When a voltage is applied, charges accumulate in the glass wall electrode and opposite charges collect near the solid/liquid interface in the conducting liquid. The resulting electrostatic force lowers the solid/liquid interfacial tension and with that the contact angle q and hence the focal distance of the lens. (C) to (E) Shapes of a 6-mm diameter lens taken at different applied voltages.
Prototype FluidFocus lenses
Photos courtesy of Philips
I remember that fluid lenses have been used by holographers for a long time, because they can be of quite high quality even with large diameter. Vari*lite also uses fluid lenses in some of their intelligent lighting fixtures.
The News here is that the Philips lens can be focused by an electric field with no part moving other then the lens. The size of their prototype is tiny; IMHO they need at least to triple the size of it to make it useful for digital cameras.
-- www.linux-laser.org - Open Source Laser Show Software for Linux
Depends on the properties of the liquids. On the left, the blue liquid is convex and the brown concanve, and on the right the blue is concave and the brow convex.
So, if light is faster in the blue liquid than in the brown one, the light-rays would move as described.
A lone researcher did it to make cheap bifocals a few years back. It is an extremely inexpensive way to provide a "one size fits all" pair of glasses for everyone who needs them. No custom lenswork needed - just pump liquid in or out :)
I guess you where sleeping your way through the optics lectures: These lenses could definitely work. If you look at the picture
you see that there are two fluids: brown one on top and a blue one on the bottom. If you remember Snell's law (ray bends towards the normal in the denser medium), you can conclude from the picture that the 'brown' fluid has a higher refractive index than the 'blue' fluid. The left picture thus resembles a hollow/concave/negative lens and the right picture resembles a convex/positive lens. Of these the positive (on the right) can be used to form a real image (one you can capture on a CCD or a retina), whereas the negative only forms a virtual image.
A colleague of mine did his internship at the group that invented these and my boss still works part-time at Philips.
karma police: arrest this man, he talks in maths; he buzzes like a fridge, he's like a detuned radio. [radiohead]
It's "lens", plural "lenses". I don't care what your dictionary says.
Ydco co
The correct saying is "fool me once, shame on me, fool me twice, shame on you".
No, it's not. If you get fooled once, it the fault of the person doing the fooling. If you're fooled twice by the same person, the fault is yours for falling for it again. Your way is completely backwards.
Want to improve your Karma? Instead of "Post Anonymously", try the "Post Humously" option.
A man designed some specs that used this technology in order to provide clear sight to the poor masses in Africa. All he did was have two syringes - one for each lens- and he adjusted the lens by pumping in/sucing out liquid as the person looked at some images, then he unplugged the syringes and a valve kept the liquid in and the glasses set to the same level. It's kind of a one-pair-fits-all system where the vast majority of people that needed glasses could use this one system. They sure weren't hot to look at, but no-one gave a crap because people aren't so vain over there! This certainly isn't a new technology.
http://www.frenchgeek.com/
I can't comment on the technology in the article, but I can say this, Philips NL are the nicest company I have ever worked for. If you are ever considering a job
at this company and wonder about their corporate culture know this... Philips combine technical excellence with an easy going attitude that encourages invention and freethinking.
They pay good wages and have excellent facilities. I was at their Eindhoven unit in 1995
for about 6 months. Even though I was an outsider brought in on consultancy, younger than my work peers, and a foreigner from England, I was treated with respect from day 1 until I left. The Dutch are very friendly, but most importantly straight talking people. I never had to endure hidden agendas and bullshit that pervades US and some UK companies. They are very open and honest. After the first night out drinking beers, I knew how the much people I worked with earned, about their families, houses, lifestyles and ambitions. One of the family straight away. Work was intense but enjoyable, you had the feeling of working somewhere that makes a difference doing proper frontier research. I hope its still like that. I was sad to go. Philips invented the CD amongst other things. They also sponser the PSV Eindhoven football team.
Big up Philips.
According to the article, it takes 10 ms to focus.
I remember this idea being used 12 years ago in Africa to make cheap glasses.
Anyone need prior art ?
OIL LENS. Force-field-enclosed hufu oil, used principally in telescopes. Oil lenses -- so accurate that they have yet to be surpassed, eight millenia after their invention -- share with many other enduring pieces of technology an elegant simplicity. Each lens is made up of a layer of hufuf oil (varying in thickness from .5 mm to 1.0 mm) held in static tension by an enclosing forcefield, and is places within a viewing tube as part of a magnifying or other light-manipulating system. Because of the extremely responsive nature of the enclosing force field, the oil layer can be adusted within microns of a desired setting. No other type of lens element approaches such accuracy.
in 7687, Marcus Vander, an Ixian Field Technician (Class 3) was experminenting with the effects of various force fields on compressed fluids. He had chosen hufuf oil (a derivitave of the hufuf plant, a native growth of Ecaz noted chiefly for its oil-filled seed pods) because of its viscosity and near-perfect transparency.
Vander wished to develop some means of transporting liquids using a force field as a container, an invention which would undoubtedly have had a wide array of useful applications. What he actually created -- as he discovered when the suspended oil focused a beam of white light onto his lab counter and melted its finish -- was the first oil lens.
The new lenses completely replaced all older, less accurate types within fifteen years of their entry into the marketplace. Their supremacy was threatened only once, in 8176, when a poor harvest of hufuf pods created a shortage of oil. Fortunately, the season following was an exceptionally good one; it was discovered that the hufufu plant adapted very nicely to cultivation on Yorba. The double cultivation has prevented any further shortages.
-- SKYKING, SKYKING, DO NOT ANSWER.
After all, I invented a variant back in '83. NASA should still have copies of some of my drawings.
.
Of course I designed it for different uses (mostly diagnostic) and had a few added features that they didn't implement. Gonna have to look at their patents and take a gander at the claims.
I wonder if I should sue.
What's *really* funny is that from what I know, DoD may already have patented my beastie for use in SDI, with or without NASA permission.
Hmmmmm . . . . .
Rustin
Data is the lever, rigor the fulcrum, brains the force that drives it all.
They had a snippet about those in Wired a couple years ago -- they were filled with some sort of oil, as I recall. They look like Harry Potter glasses, but they cost, IIRC, about a buck a pop, making them ideal for distribution in Africa and other destitute areas.
A French company called Varioptic has developed such a lens and is close to the mass production phase.
There are no moving membranes involved. The only moving parts are the two fluids. The lens is formed by a moving interface between the two. Even if some sort of mechanical shock causes this interface to break up, simply wait and the system will eventually re-equilibrate. If you take a container with water and oil and shake it up you just wat a few hours or days and the two fluids will seperate back out again. Since there really *are* no moving parts, this lens should be able to operate over an infinite number of focussings without trouble. At the least, it will be able to refocus a number of times orders of magnitude beyond what a mechanical system could handle.
The electrodes shouldn't have problems with corrosion. First, they don't even have to be in contact with the solution - the interaction is electrostatic and so a Teflon coating could be used. Furthermore, when working with a known solvent, corrosion issues are trivial. It's when making stuff that interfaces with the outside world and biological interfaces with all the associated uncontrolled variables that we still hit problems.
The curve should actually be as perfect as you want*. The interface is created by two imiscible liquids - while there will be some transient ripples from vibration, etc, the overall lens interface will be scratch free. It doesn't matter what the manufacturing quantities are - the lenses will be near perfect - the physics of the liquids will smooth out minor manufacturing defects. The only big concern would be defects in the electrodes (unlikely to be big enough in actuality to significantly affect the lenses) and making sure the correct volumes of both liquids are added. (again a trivial matter with modern liquid handling technology) Even if you do get some defects - its easy to correct. Simply automate an optical testing station where each lens has a light pattern run through it. A sensor looks for abberrations in the otpput light and calculates if the problem is fatal. If not, it calculates the necessary compensation to get proper optical performance. (eg: more or less charge on the elecgrodes for a given focus.) have an EEPROM associated with each lens that stores the correction value - problem solved.
* Note: your point holds in that the curve generated by the liquids doesn't form a perfect lens so you'll get hit with some nasty chromatic and spherical abberrations. These lenses definately WON'T be used for high quality optics.
Light loss should be a non-issue. I might be wrong here but surface reflection is primarily at air/liquid and air/solid interfaces because of the large refractive index mismatch. Here, all of the internal interfaces are liquid/liquid and liquid/solid interfaces. Reflective losses shouldn't happen, making anti-reflective coating unnecessary.
Color balance will only be an issue if the liquids absorb a particular color preferrentially. Since both liquids (at least from the pictures) appear colorless, this isn't an issue. The UV degradation you mention is an issue but simply putting a UV absorbing front coating on the lens should prevent degradation. Overall, the problem should be no worse than what one sees with low cost optics with plastic lens components.
I do agree that this lens won't be practical for anything but low-quality optics. The size is limited by the surface tensions and won't get much bigger than what is being demonstrated. Also, the lens shape is non-ideal and will give poor optical performance regardless of the size since it's shape is purely determined by the interacting surface tensions of the liquids.
What this lens will be wonderful for is low-cost disposable cameras, cell phone cameras and small security cameras where image quality isn't essential and cost/size are the determining factors.
A potential killer app is machine vision. A robot can easily compensate for the lens aberrations computationally. Furthermore, replacing the continuous ring electrode with a segmented one gives the ability to cahge the curvature
Plans are to make a Liquid Mirror Telescope (different tech: spinning Mercury) bigger than the Mt. Palomar. I think that the electronic wetting tech will probably show up in hihg-end consumer telescope eyepieces. Current variable eyepieces use mechanical components to vary the gap between multiple elements. This should be easier to manufacture. R.