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Proposed Telescope Focuses Light Without Mirror Or Lens

Soulskill posted more than 6 years ago | from the i-can-see-clearly-now dept.

Space 165

A team of scientists from Observatoire Midi Pyrénées in Toulouse, France have been working with an unusual technique for focusing light. It takes advantage of diffraction - the bending of waves when they encounter an obstacle in their path - to focus light as it passes through a foil sheet with precise holes in it. The scientists suggest that an orbital 30-meter imager could resolve planets the size of Earth within 30 light-years. In addition, the foil is much lighter than traditional materials, and thus easier to transport. "A Fresnel imager with a sheet of a given size has vision just as sharp as a traditional telescope with a mirror of the same size, though it collects just 10% or so of the light. It can also observe in the ultraviolet and infrared, in addition to visible light. The imager can take very detailed images with high contrast, which is great for 'being able to see a very faint object in the close vicinity of a bright one.'"

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Will they build it. (2, Insightful)

FiestaFan (1258734) | more than 6 years ago | (#23271630)

Great, but will it get build before I'm dead?

Re:Will they build it. (1)

calebt3 (1098475) | more than 6 years ago | (#23271678)

Yes, in the same sense that we will have practical fusion power in 10-20 years for the $BIGNUMBERth year in a row or that Duke Nukem is almost done.

Re:Will they build it. (1)

Gerzel (240421) | more than 6 years ago | (#23272024)

No.

Fusion power relies on theoretical advances and isn't really all that well known.

Refraction of light has been around since before Newton and is very well known. The only major obstacle being the materials used in building one.

Re:Will they build it. (1)

BrentH (1154987) | more than 6 years ago | (#23272082)

Fusion power relies on theories very well known, hence A-bomb since the forties/fifties. The only problem in building a fusionplant is succesfully containing all this energy and heat, which is entirely an engineering problem, and a very difficult one at that.

Re:Will they build it. (1)

Dak RIT (556128) | more than 6 years ago | (#23272350)

Fission is not Fusion.

Re:Will they build it. (1)

fractoid (1076465) | more than 6 years ago | (#23272424)

Neither is the H-bomb.

Re:Will they build it. (1)

Alioth (221270) | more than 6 years ago | (#23272758)

Modern thermonuclear weapons are fusion, not fission bombs. (They do have a fission 'detonator' though).

Re:Will they build it. (2, Interesting)

TapeCutter (624760) | more than 6 years ago | (#23272206)

"The only major obstacle being the materials used in building one."

I was under the impression that the main impediment to large refractors is the "halo" effect (coloured rings around the edge of the image), this was the problem Newton solved with the reflector and it is why Newtonian telescopes are the norm. The halo is unoticable with a small high-quality refractor (eg: binoculars) but the effect rapidly deteriorates the usefullness of refractors as the size increases.

No mention of wether this design suffers from the halo effect but radically new scope designs are rare and I like their thinking!

Of course with such a long focal length a large scope of this design would have to be space based but I don't see any insurmountable problems lanching and deploying such a beast in two parts, except of course the usual cost/benifit arguments. As for the objections elsewhere in this thread that a two part scope would drift out of sync, precisely syncronised space flight been already been done with a pair of gravity probes. Besides we also have something called adaptive optics.

Re:Will they build it. (2, Insightful)

ArAgost (853804) | more than 6 years ago | (#23272410)

Chromatic aberration is usually (in everyday optics) caused by refraction. Of course, since IIRC different wavelenghts diffract differently, there will be some problem of this kind, but still it's a neat idea.

Re:Will they build it. (2, Interesting)

Malekin (1079147) | more than 6 years ago | (#23272546)

Any aperture will cause diffraction. Reflector or refractor. The halos aren't visible in binoculars because they have magnification ratios too small.

Reflectors are preferred over refractors because it's cheaper and easier to make a large mirror than it is to make a large set of refracting optics. A larger diameter aperture will result in less diffraction but the primary motivation for large diameter scopes (and thus the popularity of reflector designs) is that a large diameter is a large "light bucket". The more light you capture, the more (dimmer) objects you can observe.

Re:Will they build it. (0)

Anonymous Coward | more than 6 years ago | (#23272672)

The "halo effect" of which you speak has a name, Its called "chromatic aberration" and is the reason why refracting telescopes are expensive to build, especially if you want a large aperture with lots of light gathering power. The solution is to build a lens out of glasses with different refractive indices. Of course chromatic aberration is only one of a number of factors that affect the final image quality.

A digression, the Newtonian reflector solves the aperture problem - its easier to use mirrors to gather the light, however, the magnification occurs in the eyepiece of a traditional reflecting rig, so the optical characteristics of lenses are still an important factor in the performance of such a telescope.

I should imagine that the plane refractor "lens" from the article uses a lot of digital processing to correct the aberrations, rather than doing it in the analogue light gathering part of the system.

Re:Will they build it. (2, Informative)

hubie (108345) | more than 6 years ago | (#23273914)

The gravity probes, as far as I am aware, do not have precisely synchronized flight, but very good knowledge of where each of them are. The science is extracted by measuring the changes in the spacecraft separation (I think the relative distance is known at the tens or hundreds of microns). Flying a separated telescope requires measuring and controlling separations and rotations to a level much more demanding than the GRACE satellites. In principle it can be done now (such as in the lab), but in practice it is very challenging (at least to do on a reasonable budget) which is why many of the NASA and ESA separated telescope projects have been drastically scaled back or delayed (SIM, TPF, Darwin, etc.).

In general, long focal lengths aren't that much of a problem because of the many telescope designs that fold up the optical path.

Re:Will they build it. (1)

mrbluze (1034940) | more than 6 years ago | (#23271688)

It can also observe in the ultraviolet and infrared, in addition to visible light.
... and if you phone in the next 30 minutes, we'll throw in a free set of telescopic steak-knives, absolutely free. That's right folks, it slices, it dices, it focuses with razor sharp precision. Still not convinced, stay tuned and watch our chef Pierre demonstrate...

Depends on your age.. (0)

Anonymous Coward | more than 6 years ago | (#23271756)

are you an old geezer, or a young whippersnapper? Or are you somewheres inbetween?

Re:Will they build it. (1)

SL Baur (19540) | more than 6 years ago | (#23272312)

This was "invented" decades ago. Prior art is the Anopticon described by Isaac Asimov. See http://www.halfbakery.com/idea/enhanced_20non_20optic_20camera [halfbakery.com]

(you have to go all the way down to the bottom to see the reference. And thank you Disney that Marooned Off Vesta isn't in the public domain now.)

Re:Will they build it. (1)

Enry (630) | more than 6 years ago | (#23272884)

It wasn't Marooned Off Vesta that had the Anopticon, it was Anniversary [wikipedia.org] written in 1959.

Re:Will they build it. (1)

ozmanjusri (601766) | more than 6 years ago | (#23272490)

Give 'em a break.

It'll take longer than a couple of weeks.

Whoops. Sorry, you weren't supposed to know that.

Re:Will they build it. (0)

master_p (608214) | more than 6 years ago | (#23273362)

*BANG* ...nope.

Looks like a sail... (4, Interesting)

sapphire wyvern (1153271) | more than 6 years ago | (#23271648)

Hmm, a large flat surface with holes in it.

It looks like launching one of these babies would require solutions to the same technical problems as solar sails, ie stowing & unfolding once in orbit.

Would it be possible to have the sheet do double duty, acting as both a Fresnel "lens" and a means of propulsion for the spacecraft? That might be a neat way of getting the instruments to a good location.

Re:Looks like a sail... (1)

sapphire wyvern (1153271) | more than 6 years ago | (#23271670)

Hmm, bad form to reply to my own post.

I note that one objection raised in the article is that since the focal length of this thing is measured in kilometres, the instruments would have to be borne on a separate spacecraft to the focussing sheet, and that keeping the two aligned when changing the orientation of the instrument would require a lot of fuel.

This seems like it would be a perfect use for the solar sail technique; hopefully it would allow you to keep the instrument craft on a pretty much ballistic course (just changing attitude) and use the solar sail to move the focussing sheet from place to place.

Quite possibly this doesn't make any sense; I don't know any orbital mechanics or the details of solar sailcraft theory. But it seems like it could be good deal.

Much more fragile than a sail (2, Insightful)

Mathinker (909784) | more than 6 years ago | (#23271842)

I think you are missing a big point here. We're not talking about a solid sheet like a sail, but rather, a sheet which is X% holes, and for which the exact geometric arrangement of the holes is critical for the physics to work. Looks to me like one has even started to think about how it can survive the stresses of being launched at multiple G's.

Errata: "one" - "no one" (1)

Mathinker (909784) | more than 6 years ago | (#23271858)

Also forgot to add: the efficiency of transmission is better as the percentage of holes gets bigger, i.e., as it gets more fragile.

Re:Looks like a sail... (1)

Plazmid (1132467) | more than 6 years ago | (#23271844)

Wow, you might have just found a big problem with this idea. The telescope requires two space craft that have to be place very precisely. Light slowly pushes the spacecraft out of place, which means they have to burn fuel to get back in position, which makes things more expensive.

Re:Looks like a sail... (0)

Anonymous Coward | more than 6 years ago | (#23271946)

Seriously, how much would it cost for the extra fuel necessary to compensate for the push of to light, 5 cents?

Re:Looks like a sail... (1)

dvice_null (981029) | more than 6 years ago | (#23272452)

Gallon of fuel: 3 dollars
Getting it to space: 3000 dollars

Re:Looks like a sail... (1)

atamido (1020905) | more than 6 years ago | (#23272164)

It sounds almost like a fresnel lens, but with parts being opaque. Wouldn't this cause diffraction patterns like in a double-slit experiment [wikipedia.org] ? Wouldn't having this pattern everywhere screw up your image?

Re:Looks like a sail... (0)

Anonymous Coward | more than 6 years ago | (#23272310)

It's the diffraction that CREATES the image.

Re:Looks like a sail... (0)

Anonymous Coward | more than 6 years ago | (#23273028)

Gee I wonder if anyone in a team of physicists had thought of that?

Better get them on the phone!

Acts like a sail (0)

Anonymous Coward | more than 6 years ago | (#23272326)

Light pressure is going to make that alignment problem about 10x worse.

ok... (4, Insightful)

fyngyrz (762201) | more than 6 years ago | (#23271656)

Make a sphere with a central axis. Place the fresnel lens on the surface of the sphere. Rotate the sphere about the center (where the focal point is.) No more formation flying, etc. Since you don't need any part of the sphere but the place where the fresnel lens is, just create a radius - lens at one end, focal point at the other end. Use a track to adjust the focal point distance from the foil. Rotate the entire assembly to re-point. No formation flying. Precision alignment all the time. Slow adjustment means good fuel economy.

It seems to me that this is a great excuse for a foil-making plant in space. Imagine a veewwwwy large foil sheet. Then think of the available resolution. This is better than a dispersed array.

Well, one can hope. :-)

Re:ok... (1)

Eivind (15695) | more than 6 years ago | (#23272342)

Except, offcourse that it's not all that trivial to create a "radius" with the fresnel-plate on one end and the camera-stuff on the other, and rotate the entire assembly quickly and accurately (to within less than a mm) when the radius is a dozen miles long. Indeed, unless the "radius" is a rod of unobtanium, flexing and bending is going to make it completely impractical.

Re:ok... (0)

Anonymous Coward | more than 6 years ago | (#23272400)

Well, since you don't really need a radius either, just make a track several km long, launch it into space, and stick the lens on one end, and the camera on the other. I imagine tracks with lengths measured in kilometers have their own problems though.

Re:ok... (1)

Electric-PI (1021677) | more than 6 years ago | (#23272488)

Make a sphere with a central axis. Place the fresnel lens on the surface of the sphere. Rotate the sphere about the center (where the focal point is.) No more formation flying, etc. Since you don't need any part of the sphere but the place where the fresnel lens is, just create a radius - lens at one end, focal point at the other end. Use a track to adjust the focal point distance from the foil. Rotate the entire assembly to re-point. No formation flying. Precision alignment all the time. Slow adjustment means good fuel economy.

from the article:

For one thing, the light comes to a focus far away from the foil sheet â" with distances measured in kilometres

So how big would that sphere be? A better idea maybe to place the whole setup on a planetary system such as the dark side of the moon or possibly mars or further. Of course it still has to be brought there and setup. This makes it more difficult and I agree with the last part of the article that it's not a matured enough yet.

The Dark Side Of The Moon (1)

Fleetie (603229) | more than 6 years ago | (#23272994)

"... the dark side of the Moon"?

Got Brain Damage, have we?! I see the pigs are on the wing again!

I mean sure, there is always a DSOTM, but the pesky thing is always moving!

BTW, who reckons that Waters' recent errant flying pig was a deliberate stunt; a reprise of the simimar incident in London in 1976 (IIRC); and NOT an accident?

Re:ok... (0)

Anonymous Coward | more than 6 years ago | (#23272628)

The bit you missed is that the focal length is on the order of a few kilometres. That's a BIG sphere you've got there..

Re:ok... (0)

Anonymous Coward | more than 6 years ago | (#23273592)

Your "radius" would need to be kilometers long.

two words (1)

Swampash (1131503) | more than 6 years ago | (#23271662)

"anoptikon"

Re:two words (1)

johannesg (664142) | more than 6 years ago | (#23272012)

That's ONE word.

Re:two words (1)

jd (1658) | more than 6 years ago | (#23272020)

Sorry, but unless there are three of you and you have photographs proving you can get drunk on water, I cannot accept your claim.

Re:two words (1)

Swampash (1131503) | more than 6 years ago | (#23272258)

*golf clap* :)

Re:two words (1)

A Pressbutton (252219) | more than 6 years ago | (#23272174)

There was a really good Asimov short story about this IIRC

Re:two words (1)

Arancaytar (966377) | more than 6 years ago | (#23273500)

Yes, it was called Anniversary. A sequel to Marooned off Vesta.

Problems (4, Funny)

FearForWings (1189605) | more than 6 years ago | (#23271686)

I think it would be clear to anyone who examines it, the idea clearly has some holes in it.

Re:Problems (1)

Whiteox (919863) | more than 6 years ago | (#23271940)

Not to mention all the additional ones caused by space debris, tiny meteors, even bigger meteors, alien spaceships and really, really big meteors.

Re:Problems (1)

skeeto (1138903) | more than 6 years ago | (#23273456)

Didn't they already put a satellite up without the optics? I believe it was called the Hubble something-or-other.

I discovered that as a kid .. (2, Informative)

Saffaya (702234) | more than 6 years ago | (#23271696)

.. when I didn't have my glasses handy and still wanted to look at something in particular.

I would form a small hole by curling my index then look through it for visual correction to my myopea.

Re:I discovered that as a kid .. (1)

evanbd (210358) | more than 6 years ago | (#23271776)

You discovered the pinhole camera, aka tiny aperture = increased depth of field. This is different -- they actually have a large imaging aperture and still keep good focus.

Re:I discovered that as a kid .. (1)

scottrocket (1065416) | more than 6 years ago | (#23271880)

Edmund Scientific used to carry a pair of "glasses" that did something like that: Each "lens" was opaque, & had a series of pinholes, like a cluster of camera obscura/pinhole cameras put together.

Re:I discovered that as a kid .. (1)

Fotherington (962601) | more than 6 years ago | (#23272916)

Hey, I do that too - and teach it to others. I came across it described as an old mountaineer's trick in one of Louis de Bernières' Latin American novels. Still comes in handy when working out whether to run for a bus or not.

Re:I discovered that as a kid .. (1)

MeditationSensation (1121241) | more than 6 years ago | (#23273538)

What you didn't realize was that it made you look like a complete dork!

Not for amateurs... (4, Interesting)

syousef (465911) | more than 6 years ago | (#23271702)

I was thinking hey neat till I read this in the article.

For one thing, the light comes to a focus far away from the foil sheet - with distances measured in kilometres, which means the camera and other instruments have to be mounted on a separate spacecraft. The instrument spacecraft would have to stay precisely aligned with the foil sheet, to within a millimetre or so.

Certainly not impossible, and still exciting, but this isn't going to be a mainstream or amateur tool any time soon.

Looks like there also may be a related patent to get past...

http://www.patentstorm.us/patents/6375326-claims.html [patentstorm.us]

Patent reference seems totally unconnected (1)

Mathinker (909784) | more than 6 years ago | (#23271918)

IANAL, but at least from a technical point of view, the patent you cite seems to have little to no relevance here:

1) It deals with using a Fresnel lens, not a zone plate,
2) It's main point is using, for a single imaging, one Fresnel lens twice via having two separate optical paths through it.

Looks like it might possibly be an interesting patent, but it's not connected with the idea for this telescope (unless the Fresnel lens cited in the article, which corrects the chromatic aberation of the zone plate, is used in the fashion cited in patent, which doesn't seem likely to me).

Re:Not for amateurs... (1)

jlowery (47102) | more than 6 years ago | (#23273144)

I was thinking hey neat till I read this in the article.
Quit reading the articles!

Re:Not for amateurs... (2, Insightful)

Overzeetop (214511) | more than 6 years ago | (#23273322)

This is also somewhat complicated by the actual performance of objects in orbit. A project I worked on had two satellites in LEO - one main sat with a laser ranger, and one passive "following" sat with a corner cube. By ranging the distance between the two, the earths gravitational field could be mapped very accurately. In other words, two satellites in the exact same orbit will vary in distance with one another constantly throughout an orbit based on the gravitational field. As the orbit precesses, the variation will change from orbit to orbit.

I don't know how this would be dealt with, but it's a bit of a potential stumbling block. (well, that and getting a thin, light, high precision piece of anything into orbit without damaging it)

Re:Not for amateurs... (2, Insightful)

Luyseyal (3154) | more than 6 years ago | (#23273756)

These large earth-finder telescopes are all being proposed for Lagrange points, not LEO. However, I do wonder how big the fudge factor is for being sufficiently close to the Lagrange. E.g., if these satellites are both +/- 15km with the actual point in the middle, will the shearing effects of gravity be too much for attitude correction for such a sensitive scope?

Not an astronomer... yet.
-l

Re:Not for amateurs... (1)

marcosdumay (620877) | more than 6 years ago | (#23273374)

Well, it would take a long time until amateurs could send things into space anyway.

Also, aligning 2 satelites isn't easy even for professionals.

Re:Not for amateurs... (1)

Luyseyal (3154) | more than 6 years ago | (#23273816)

Hrm, amateurs launching things into space... I wonder if anyone's done that [amsat.org] . Does hopping a ride on someone else's rocket count as long as it's your satellite?

-l

Sounds good on paper... But (1)

Phoenix-IT (801337) | more than 6 years ago | (#23271718)

According to TFA the slotted lens would be much lighter but also MUCH MUCH larger than traditional setups. Also, the distance between the lens and the camera is so large that a second spacecraft is needed. Trying to maintain the alignment of two spacecraft would be difficult at best. Now consider that they would need to fire thrusters and move one of them every time they need to focus on a different object. How much fuel would be used up just looking at 10 different objects? I would expect a lot. Add to this what micro-meteors and the random castaway screw driver would do to the foil over time and you can see some real limitations to this. Not saying it's impossible, just that they need to work out some ways around the obvious problems.

Absolutely, completely off-topic (0, Offtopic)

line-bundle (235965) | more than 6 years ago | (#23271758)

Has there been a severe rationing of mod-points recently?

Perhaps the mod-point crisis is related to the credit-crisis?

Re:Absolutely, completely off-topic (1)

Plazmid (1132467) | more than 6 years ago | (#23271824)

Perhaps people are redeeming their mod-points for money.

Re:Absolutely, completely off-topic (1)

TapeCutter (624760) | more than 6 years ago | (#23272070)

Dunno, I've had two instance of "you have 10 mod points" in the last month or so but they vanished before I could use 'em. Kinda surprising since previously they were always in lots of 5 and not so close together.

Re:Absolutely, completely off-topic (1)

Megane (129182) | more than 6 years ago | (#23273078)

Your mod points expire after 3 days. [slashdot.org] Use 'em or lose 'em.

And I don't know why they bumped it up to 10 points at a time. The FAQ still refers to "5 points".

Re:Absolutely, completely off-topic (1)

TapeCutter (624760) | more than 6 years ago | (#23273530)

Not to put too fine a point on it but I understand the system and read /. more or less daily (currently 3525 commets). I'm damm sure both the "You have 10 points, use 'em or lose 'em" didn't last more than a day.

"And I don't know why they..."

Beats the shit out of me too, but there you have it. I've also noticed that over the past month the pages are sometimes slow to load, and I mean really slow like prehistoric 9600 dial up.

This is crazy (2, Interesting)

Plazmid (1132467) | more than 6 years ago | (#23271816)

So basically they're building A HUGE FRAKKIN' PINHOLE CAMERA. Frankly I find it strange that they would build a telescope that only collects 10% of the light, as this might present problems for planet finding. Not to mention that huge sheets of foil tend to crinkle and are susceptible to micro-meteoroids. But, if they could make it cheap enough, they could launch a bunch of them and do "brute force astronomy."

Re:This is crazy (2, Informative)

evanbd (210358) | more than 6 years ago | (#23271886)

10% of the light from a 30 meter telescope is the same amount of light as a regular 10 meter telescope. Hubble is a 2.4m telescope. I think it will have plenty of light.

Foil doesn't have to crinkle. Look at the center of a mylar balloon -- not exactly crinkly. Obviously if you want telescope-grade not-crinkly you'll have to spend a bit more, but that's not really a problem. This is also a bit more sophisticated than a pinhole camera -- those have trouble collecting much light.

Not a pinhole camera (1)

Moraelin (679338) | more than 6 years ago | (#23272252)

Heh. That's not even freaking close to "A HUGE FRAKKIN' PINHOLE CAMERA."

It's actually closer to Fresnel lens [wikipedia.org] , sorta. Well, not really, but just to get the idea started that you can use something very thin to the same effect as a bulky normal lens or telescope. This one actually a Fresnel zone plate [wikipedia.org] It uses light Interference [wikipedia.org] to act more like a lens, although it is really just a special pattern of lots and lots of pinholes.

If you will, it's closer to the double-slit experiment [wikipedia.org] in light interference that surely you must still remember from school. Behind the panel with the slits, light gets to act funny: you get zones that get more light, and zones which gets less. Photons bend their paths in certain (statistically) predictable ways.

It turns out that if you use some carefully calculated concentric circles as slits, you can actually get the light interfering in such a way, that it's actually focused like with a lens. Essentially those dark and bright bands turn into just one bright dot at the right distance. Well, having concentric holes in a thin foil is kinda hard, but these guys figured out that you can use lots and lots and lots of pinholes instead.

Anyway, even the most summary read of TFA or even the summary would have provided the hint that it's about lots of holes and interference. Which should have been plenty of hint that it's nothing like a pinhole camera. Unless, of course, you actually built a camera with sieve-like Fresnel zone plates before and mistakenly called it a pinhole camera. But I'm fairly sure that you didn't ;)

Re:Not a pinhole camera (1)

tenco (773732) | more than 6 years ago | (#23272868)

mod parent up. It's really more like a fresnel lens and nothing new. This concept for making lenses thinner and lighter is known for ages: Fresnel lens [wikipedia.org]

Re:This is crazy (4, Informative)

Genda (560240) | more than 6 years ago | (#23272462)

This is actually a really clever solution to a number of thorny problems. The first being, how do you get a really big telescope into space without breaking the bank??? Another being how do you get great contrast to show up faint sources?

  1. A) Not a Pinhole camera, It uses difraction caused by wave interaction through the holes of the lense.
  2. B) The lens has an aperture of 30 meters, with a surface area of over 700 Square meters. Even at 10% transmission, it would have more than 15 time the light gathering power of the Hubble, and more than 150 times the resolution.
  3. C) The best way to transport the lense would be to wrap the foil on a cylindrical spindle keeping it free of wrinkles, then having it unwound onto some kind of frame for mounting and stretching.
  4. D) It would have to be placed in some kind of protection housing to prevent damage from space debris.
  5. E) It would have to use some kind of laser/optical alignment system to get the lense and camera operating in conjunction. However this is not a big problem, long baseline interferometry in space would require much stricter positioning for constellations of satellites and such devices are already on the drawing boards.

In short, this is a perfectly viable technology, and it poses a fascinating solution to a really challenging problem.

Bravo!

Re:This is crazy (1)

LiquidCoooled (634315) | more than 6 years ago | (#23272900)

Depending upon how you build it, you could have an entire roll of foil lenses available and just wind the roll on when the current item gets too damaged.

Of course limit the chances by using a partial enclosure, but since some of it must be open to space then its wise to have spares.

more fun with diffraction (3, Interesting)

heeeraldo (766428) | more than 6 years ago | (#23271846)

Canon has been using the same principle in a couple of lenses [canon.com] for some time now. The lenses themselves are pretty damn expensive but well regarded; I hope the telescope meets similar success.

Re:more fun with diffraction (0)

Anonymous Coward | more than 6 years ago | (#23272114)

Those Canon lenses are based on the more conventional Fresnel lens [wikipedia.org] design, in which the lens effectively has cylindrical sections of solid glass removed from inside the lens to create a sawtooth surface. They don't use diffraction by an array of pinholes.

Re:more fun with diffraction (0)

Anonymous Coward | more than 6 years ago | (#23272896)

You're correct that it's not a zone plate, and therefore not very connected to the article, but their idea of using two complementary Fresnel lenses separated by an exact distance (which seems to cancel a lot of the distortions) is pretty cool!

Re:more fun with diffraction (1)

Life Jockey (875670) | more than 6 years ago | (#23273122)

I was using this principle over 50 years ago ... it's called a pin hole camera... centuries old discovery.

Re:more fun with diffraction (1)

cyfer2000 (548592) | more than 6 years ago | (#23273858)

In X-ray optics, we actually use bent crystals like silicon, germanium, diamond, graphite or multilayer to focus X-ray by diffraction for maybe 50 years. A short paper on the multilayer for X-ray optics I found at Argonne national lab is available at here (PDF) [anl.gov] .

Exoplanets (1)

QuantumG (50515) | more than 6 years ago | (#23271864)

In the first 8 years of the 21st century I have witnessed an almost feverish acceleration of astronomer attention on the discovery of "exoplanets" [exoplanets.org] - planets around stars other than our own Sun. Already some solar systems very similar to our own have been discovered and some tentative measurements of the atmospheric content of these planets is underway. I believe it is only a matter of months or years before an oxygen-rich "earth-like" planet is discovered. Prognosticator of prognosticators that I am, I'll even go so far as to suggest a date: before the end of 2012.

But who cares when it happens, if it does happen, what then? What next? Will there be any debate that the concentration of oxygen implies that life is present on this newly discovered world? Will it take the imaging of an exoplanet to "prove" that life exists elsewhere in the universe? Will it take more?

And finally, will anyone care? Not the geeks. Not the astronomers or the scientists or the science fiction writers, but the average person on the street. At the time of writing, each exoplanet discovery is treated to an orgy of poorly understood journalism. It seems the idea of "planets around other stars" is something the mainstream audience can understand just enough and goes well to fill that slot in the news between the sports and the weather. Will this fad wear off by the time the startling discovery of exoplanet life is made? Or worse yet, will such an amazing discovery get exactly the same amount of coverage as the average exoplanet discovery gets now?

Ultimately the whole thing could be a terrible disappointment. Imagine, for a moment, that not only do astronomers discover life on an exoplanet but they actually discover intelligent life on an exoplanet. Pretty little pictures of roads and factories, ships at sea, planes and rockets in flight. Some serious questions would need to be directed towards the SETI program.. as it seems highly unlikely that a modern society could exist without emanating some signals that SETI should have picked up. Maybe a thorough search of the archives will reveal that many possible signals from that part of the sky were ignored accidentally.

In any case, now that we know they're there, how do we go about contacting them? Should we? Who gets to decide? Is that a pointless question as there's just no way to stop someone from sending a signal if they want to? And then there's the long long wait for the signal to get there and maybe no-one is listening or maybe the signal is too corrupted or just not decipherable by an alien mind. Decades may pass with no message returned. The general public will lose interest. Can you imagine?

Re:Exoplanets (1)

flargleblarg (685368) | more than 6 years ago | (#23271900)

> In the first 8 years of the 21st century I have witnessed [...]

Well, actually, the first 8 years of the 21st Century aren't over yet. In eight months they will be, however.

Re:Exoplanets (1)

FinestLittleSpace (719663) | more than 6 years ago | (#23272526)

Incorrect!
2000
2001
2002
2003
2004
2005
2006
2007

I count EIGHT years. Don't ever forget the golden zero...

Enough about Y2K! (1)

Mathinker (909784) | more than 6 years ago | (#23272930)

This one-off controversy about when the millenium started [wikipedia.org] is getting a little old, no?

Yeah, I know, "no one likes a math geek" ...

Re:Exoplanets (1)

Ihlosi (895663) | more than 6 years ago | (#23271904)

Some serious questions would need to be directed towards the SETI program.. as it seems highly unlikely that a modern society could exist without emanating some signals that SETI should have picked up.



Right now, SETI isn't really looking for "random" signals. It's looking for signals deliberately sent our way, with plenty of power. So it wouldn't really be surprising if they're not picking up TV signals from Alpha Centauri.

Re:Exoplanets (1)

TheLink (130905) | more than 6 years ago | (#23272044)

What they should actually do is start building those spinning space stations that people can actually live on long term without "wasting away" due to weightlessness or getting radiation sickness.

Once you can do that, then you can send people to Mars or the asteroid belt. People are no longer stuck on earth - they can feasibly live in space.

Then people can build telescopes in space if they want - even if it takes a while - the sun and asteroids will be around for quite some time still.

As it is, I think we're doing things the wrong way round - talking about building huge telescopes in space, going to Mars etc. Like trying to jump before being able to crawl or walk.

A space elevator would be nice, but perhaps it's easier to do the space station stuff first.

Re:Exoplanets (1)

QuantumG (50515) | more than 6 years ago | (#23272072)

It's all about funding dude.

Life on other worlds (1)

jd (1658) | more than 6 years ago | (#23272156)

The life question is easy. James Lovelock demonstrated that planets devoid of life will have a composition totally distinct from any planet bearing life. You do not need to know what the life is, the chemistry, the complexity, etc. You need only look at the stability of the system. Stable systems have no life. Unstable systems do. Indeed, he demonstrated by means of the Daisyworld hypothesis that in order for a system containing life to remain containing life, the life on it must alter the system so as to provide negative feedback on desirable attributes, and the reduction in that organism increases its viability. This must take place with a chemistry that is unstable in the environment, or it'll overrun the environment and wipe itself out. Any other dynamic is self-destructive.

What you want to look for is not a planet with X, Y or Z in terms of chemical components in the atmosphere, but evidence of a dynamic equilibrium actively maintained by a minimum of two opposing negative feedback loops that involve highly unstable components in the atmosphere. Since there will be day and night, and seasons, different points on the planet will register different prevailing feedback loops. These conditions cannot arise in a wholly inorganic environment. An inorganic environment may be chaotic (the atmospheres of Saturn and Jupiter, for example) or very basic (as in the case of the surface of Pluto) but the systems are relatively basic. They are simple chemical systems, passively reacting to the occasional direct strike by a comet, but there is nothing metastable or unstable about any of those examples. If anything, they are remarkable in their stability.

It is planets whose chemistry should be violently unstable but are actively held in dynamic equilibrium that are interesting. Those have processes that are in the realms of what we would consider living matter, and outside the realms of the non-living.

What about intelligent life? First define intelligence, and then secondly prove there's any on Earth. If we don't know what we're looking for, or how to recognize it if we find it, then such a search is futile. I regard SETI as more of a research lab for advanced theories into digital signal processing. It won't be useful until the one kilometer array is active, and the planned closures in Britain inclclude key parts of that array. We also need very very powerful signals processing - a million channels, or even half a billion, isn't much. We don't even know if we want the radio or optical spectrums. So, two arrays - one radio, one optical - at a kilometer diameter and, oh, say a trillion channels being monitored and analyzed with rather better signals theory than SETI@Home use. When will this happen? Never. That, then, is the earliest alien intelligence can be passively detected by us.

Re:Exoplanets (1)

erroneus (253617) | more than 6 years ago | (#23272210)

Yes, it's probably because of George W. Bush... ...probably just about the only way to get away from him.

Seems that there may be a little problem (1)

Whuffo (1043790) | more than 6 years ago | (#23271908)

This isn't a pinhole camera - it's a giant diffraction grating that acts as a lens. What I can't figure out is how they're going to keep the "lens" accurate; very small bumps / wrinkles in the foil would disrupt the operation of the lens, so it'd have to be kept flat (or curved to a specific radius) constantly. That's going to be very difficult to do.

This looks good on the drawing board but making a real-world example is going to require some very fancy engineering. Building larger scale structures in space isn't as easy as many think; there's gravitational gradients, solar wind and more out there. Forces that are tiny - but when these tiny forces are applied (unevenly) to a large structure the total forces can be very impressive (and destructive).

Re:Seems that there may be a little problem (0)

Anonymous Coward | more than 6 years ago | (#23272102)

spin it around its optical axis perhaps? just kidding.

Much more fragile than a sail (1)

clint999 (1277046) | more than 6 years ago | (#23271954)

Canon has been using the same principle in a couple of lenses for some time now. The lenses themselves are pretty damn expensive but well regarded; I hope the telescope meets similar success.

Not practical (1)

searob (1147641) | more than 6 years ago | (#23272124)

The logistics of maneuvering two satellites (kilometers apart) to stay aligned would be daunting. More research needs to be done to decrease the focal length.

Misleading Title.....Again..... (1)

IHC Navistar (967161) | more than 6 years ago | (#23272176)

From the article: "It does not require a large primary mirror or lens, though it does use a smaller secondary mirror and lens."

So it *DOES* use a LENS AND MIRROR to focus light. Honestly, when will journalists, and scientists, stop making claims that are obviously NOT true?!?

That's good, and all (1)

Haoie (1277294) | more than 6 years ago | (#23272200)

It's good and all to look at the stars, but when is mankind ever going to reach them?

Re:That's good, and all (1)

Gavagai80 (1275204) | more than 6 years ago | (#23272322)

As soon as someone volunteers for a one way, 40,000 year trip.

YUO FAiL It! (-1, Flamebait)

Anonymous Coward | more than 6 years ago | (#23272278)

My be3post up my [goat.cx]

Only advantage is the light weight (2, Interesting)

helioquake (841463) | more than 6 years ago | (#23272404)

The article makes it sound like only a 30-meter "Fresnel" optics can allow to resolve an earth-size object within 30 light-years.

The fact is that any conventional 30-meter telescope can resolve an earth-size object within 30 light-years (circa 6000Angstrom in wavelength). Spatial resolution can be determined by the ratio of wavelength to diameter of the optics:

    6000A / 30m ~ 2e-8 radian ~ 0.004 arcsec.

So a 30m telescope can resolve an object in angular size of 0.004arcsec at 6000Angstrom.

At the distance of 30 light-years, the earth-size object looks like

    6400km / 30lyr ~ 2e-8 radian ~ 0.004 arcsec.

So that's that. This telescope doesn't give us any special resolving power per optics size. So the advantage is merely its light weight.

Since the precise alignment of holes is required for this optics to work, I can see why this project got kicked out by ESA. It's probably too premature to attempt in deploying this kind of precision engineering in space today.

Re:Only advantage is the light weight (1)

FiestaFan (1258734) | more than 6 years ago | (#23272738)

Whats that in pixels?

Re:Only advantage is the light weight (1)

19thNervousBreakdown (768619) | more than 6 years ago | (#23273752)

One.

Extra holes (0)

Anonymous Coward | more than 6 years ago | (#23272486)

You would still have to protect the foil sheet somehow from micro particles & space junk punching extra holes in it ruining the focus....

What's unusual about fresnel lenses? (1)

argent (18001) | more than 6 years ago | (#23272648)

They're already widely used down here on Earth.

Re:What's unusual about fresnel lenses? (1)

TeknoHog (164938) | more than 6 years ago | (#23272732)

The article is about Fresnel zone plates [wikipedia.org] , which are quite different from lenses. You can use any opaque material to make a FZP, whereas a lens must be made of transparent material.

Use Saturn's rings instead. (1)

Richard Kirk (535523) | more than 6 years ago | (#23272950)

Why settle for a piddling 30 meters? Saturn's rings have a certain zone-plate like flavour to them. With a few artificial shepherd moons to tweak the periodic intervals, weought to get some sort of an interference pattern. The focal length will be huge so the rings don't have to be flat...

Actually, this is pretty silly, but it might be possible to make a partially self-assembling zone plate out of a massive central body and a carefully seeded orbiting cloud of black dust, edge-on to the sun. You might be able to get a refractive zone plate using orbiting gas, but you would have to control the optical retardation, where black is just black and if it is black in the right places, then it might work.

For another fun sort of lens, see http://en.wikipedia.org/wiki/Luneberg_lens [wikipedia.org]

Why not just (1)

vikstar (615372) | more than 6 years ago | (#23273336)

make the foil into a parabolic shape to reflect light to a camera instead of cutting holes in it to defract light to a camera much further away?

What about a detector a few hundreds klicks away? (1)

clonan (64380) | more than 6 years ago | (#23273766)

IT occurs to me that is the focal length is THAT long we could put these very large systems in space and have a smaller GROUND based detector.

Simply put the thing in GEO orbit and point it at a receiving station. This will dramatically increase the "lense" size.

Of course you will get some interference from the atmosphere but this can be activly compensated.
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