Gradient Index Lens Explained
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- Опубликовано: 25 авг 2024
- This is short is about how a Gradient Index Lens (or GRIN lens) works compared to how a normal confocal lens with curved glass interfaces operates.
The diffraction inside the lens is probably due to the fact that the refractive index gradient is not exactly correct. The total gradient is approximated from 5 linear gradients instead of 1 smooth circular gradient. This is probably the reason for the observed interference pattern observed.
The simulations were made using the code supplied by @DiffractionLimited
Music: Nebular Focus by Dan Henig
#optics #light #physics
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"I know, so cool" 😂 absolutely did not expect that amount of eroticism in a video about lens
But it actually IS so cool! How do they get the optical density gradient be so perfectly curved?
We have a weird and exotic problem in the ultrahigh power laser world where essentially everything can become a GRIN lens. If you crank the intensity of a beam up high enough, eg. into the gigawatt per sq. cm range, the electric field component of the EM wave will actually change the local index of refraction of the glass it's traveling through (the Kerr effect) and the beam will spontaneously FOCUS ITSELF (due to gaussian intensity profile across the beam diameter) down to a point where it exceeds the damage threshold of the glass and forms a track of micron sized bubbles through it as it oscillates thousands of times between Kerr lens self-focusing and plasma bubble induced defocusing. Large numbers of "angel hair" tracking lines of damage thus accumulate in optics used in high power lasers for eg. nuclear fusion research.
That’s so cool… yet it’s probably an annoyance to you for your work
Is there a way to cause that on purpose with a much lower powered laser?
Some materials are very good at achieving this effect because they have a high value of the third-order nonlinear susceptibility. They are used on purpose achieve this effect, for instance in Kerr-Lens modelocking which is a common way to create ultrashort laser pulses.
So cool. 🤩😍
Will you do a video on how to do simulations like this?
look at their full videos, there is more simulation where that came from
Lol I've been sitting around thinking about how it might be possible to have a gradient of different materials in optics and all the sudden this video pops up. Great timing.
I first read about these in the 19seventies made by the Japanese company. Nippon sheet. Applications are mainly in the field of endoscopy where rods of the lengths of 5 to 10 cm can transport the picture. They are an alternative to the Hopkins Relay, however the latter is quite complicated in comparison to what the mechanical precision requirements concern. The GRIN lenses on the other hand are prone to inaccuracies because of the hard to control ion exchange processing of the making the circular refractive index gradient.
There are a couple of manufacturers making/using them in optical instruments, e.g. the company GRINTECH in Jena, Germany.
the flat lens give me chills 💀
That is why this video is rated for kids over 18.
out of curiosity, what's the manufacturing process like on a gradient index lens like this? i can picture the process of creating a convex or concave lens, starting with a blank and removing material until you have the right shape, but this type of lens is very unintuitive to me, especially to do precisely. best guess is it has something to do with the heat treating of a material with a refractive index that changes depending on how long/at what temp it's been anealed? or maybe it's just extruded like that? but that strikes me as too imprecise.
The Wikipedia page on "gradient index optics" gives several options to create a refractive index gradient in glass. I think what they do in practice is: introduce an accurate gradient in a thick rod of glass and then extrude it to a 1-1.5mm thick strand/wire (this is generally the diameter of a gradient index lens), cut up the glass wire and then grind and polish the ends of the short pieces to create individual lenses. But I never made them myself so I'm not certain that this is actually the way that they do it.
How about that. Maybe a glassblower could make one by layering sheets of different index glass around a cylinder and stretching it out by hand.
for microwaves, they can be 3d printed with novel materials.
Traditionally they're made by drilling holes into a dielectric material and changing the ratio of air to dielectric gradually
I recall reading a paper many years ago on using a tube with air/gas with a radial temp distribution as a lens. It worked but I'm sure keeping the "lens" consistent is a nightmare.
What software are you using for these stunning simulations??
See @DiffractionLimited channel.
I got AirPod, the whispering moment was insane
Once I've seen strange piece of glass with flat interfaces in lab. I've wonder how it works and now get it.
But how this made?
Super cool...
The end; I laughed my ass off.
Check out Machining and Microwaves! He's done videos about gradient index lenses for microwave applications, including a super cool tour at Rogers!
Thanks, it looks like an interesting channel!
why is there a gentle curve on the edges of the focused light with the first lens
Do you know why the light intensity pattern is different after the focal point compared to before the focal point. I would intuitively expect this to be symmetrical?
What would be the benefit of a cylindrical lens VS a traditional one?
You can make a lot of very small lenses with a short focal length cheaply in a large batch.
why is the light bending even before it hits the lens? Is that an animation error or is that something that happens IRL?
That is diffraction originating from the edges of the light/wave source. It can be avoided by making the source larger, but it is not really influencing the results much.
@@HuygensOptics ah ok
I almost fell off my chair in the end. Thank you.
Is this the result of Fermat's Principle of Least time?
HOW? How do you vary the refractive index in that gradient fashion? Maybe stuff dissolved in water? Is this actually used in real life? SUPER COOL!
Am I correct in thinking that one could combine shape and variable refractive index gradient to create a lens where the focal point depends on the angle of incidence of of the incoming light within a certain range?
Hey Huygens, is it possible to use this gradient technique to produce a tube instead of a rod where the gradient is radialy instead radialy? Where you get a increasing Dioptrien by turning the tube but in the tube the focal point stays the same and out side the tube it varies in distance?
What applications do these have?
How do you simulate?
And now please expand to a rod lens array 😊
Lmao I know.... this makes me think, surely it's possible to have the focal point inside the lense or exactly on its exit surface? Could a CCD/CMOS sensor then be directly cemented to the exit surface? What would happen?
That is basically what they do in interferometers: cement them directly to a beam splitter to avoid two additional (reflective) interfaces.
and how do you make an index gradient?
Wikipedia > gradient index optics > manufacture
@HuygensOptics Dear Mr. Optics, I was enjoying your short in peace when without warning, things turned hilarious. As it happened, I was not drinking coffee. Had I been, your reverb-laced hijinks might have cost me a perfectly good monitor and keyboard. Since you had no way of knowing my coffee status at the time of viewing, I can only assume you have a callous disregard for the well being of most of my desktop. GRINs might be “so cool” but I can assure you watching helplessly as warm brown liquid disappears into every crack and crevice of my monitor and all those gaps between keys on the keyboard, it’s… I am without words.
It goes without saying that you should never drink coffee while operating a sensitive electronic device.