Imaging at a trillion frames per second | Ramesh Raskar

Translator: Joseph Geni Reviewer: Thu-Huong Ha

譯者: Yilun Zhou 審譯者: Hsin Haydn

Doc Edgerton inspired us with awe and curiosity

Edgerton博士用這張子彈擊穿蘋果的照片

with this photo of a bullet piercing through an apple,

激起了我們的敬佩和好奇，

and exposure just a millionth of a second.

這張照片的曝光時間只有一百萬分之一秒。

But now, 50 years later, we can go a million times faster

但現在，五十年後，我們可以在快一百萬倍，

and see the world not at a million or a billion,

也就是不僅在一百萬分之一秒，

或者十億分之一秒，

but one trillion frames per second.

而是在萬億分之一秒見捕捉到世界。

現在我給你展示一種新型照相技術，

I present to you a new type of photography,

femto-photography,

叫做飛秒成像，

a new imaging technique so fast

這是一種技術太快以至於

that it can create slow motion videos of light in motion.

它能捕捉到光的運動。

And with that, we can create cameras that can look around corners,

所以用這個技術，我們可以制造

能看到光路拐角的照相機，

beyond line of sight,

能看到視野之外

or see inside our body without an x-ray,

或者不用X光就能透視我們身體的照相機，

這種相機挑戰了我們對於照相機的定義。

and really challenge what we mean by a camera.

Now if I take a laser pointer and turn it on and off

現在，如果我用一個激光筆，

in one trillionth of a second --

並且在萬億分之一秒內開關一次——

which is several femtoseconds --

也就是幾飛秒——

I'll create a packet of photons barely a millimeter wide.

我就會制造一些光子，

這些光子僅僅是幾毫米寬，

And that packet of photons, that bullet,

並且這些光子，像子彈一樣，

will travel at the speed of light,

會以光速前進，

and again, a million times faster than an ordinary bullet.

也就是比子彈速度高一百萬倍。

Now, if you take that bullet and take this packet of photons

現在，如果你把這個子彈，這些光子

and fire into this bottle,

打入這個瓶子裏，

how will those photons shatter into this bottle?

這些光子會怎麽樣撞擊瓶子？

How does light look in slow motion?

光在慢動作下會是什麽樣？

[Light in Slow Motion ... 10 Billion x Slow]

Now, the whole event --

現在，著整個事情—— (鼓掌)

(Applause)

(鼓掌)

Now remember, the whole event is effectively taking place

現在，請記住，這整個事情

其實是在一納秒內發生的

in less than a nanosecond --

that's how much time it takes for light to travel.

——也就是光走的時間——

But I'm slowing down in this video by a factor of 10 billion,

但現在我再把這個錄像放慢一百萬倍

so you can see the light in motion.

讓你看到運動中的光。

(Laughter)

But Coca-Cola did not sponsor this research.

但可口可樂可沒有資助這個實驗。 (笑聲)

(Laughter)

Now, there's a lot going on in this movie,

現在，在這裏有很多事會發生，

so let me break this down and show you what's going on.

所以讓我一件一件的展示。

So the pulse enters the bottle, our bullet,

現在，光束進入瓶子，也就是我們的子彈，

with a packet of photons that start traveling through

穿過瓶子，

and that start scattering inside.

並且在內部散射開來。

Some of the light leaks, goes on the table,

一些光流了出來，到了桌子上，

and you start seeing these ripples of waves.

所以你開始看到這些波紋。

Many of the photons eventually reach the cap

許多光子最終到達了瓶蓋處

and then they explode in various directions.

並且向四周散去。

As you can see, there's a bubble of air

你能看到，這裏是一個空氣泡，

and it's bouncing around inside.

它在裏面反彈。

Meanwhile, the ripples are traveling on the table,

同時，波紋也到了桌子上，

and because of the reflections at the top,

並且因爲在頂部的反射，

you see at the back of the bottle, after several frames,

你能看到在瓶子底部，幾幀之後，

反射彙聚了。

the reflections are focused.

現在，如果你用普通的子彈

Now, if you take an ordinary bullet

and let it go the same distance and slow down the video --

走同樣的路程，平且放慢視頻，

again, by a factor of 10 billion --

同樣是一百萬倍，你知道

do you know how long you'll have to sit here to watch that movie?

你需要等多久來看到這個全過程嗎？

(Laughter)

A day, a week? Actually, a whole year.

一天，一周？實際上，是一年。

It'll be a very boring movie --

這當然會很無聊 (笑聲)

(Laughter)

of a slow, ordinary bullet in motion.

一個慢的，普通的子彈運動錄像。

And what about some still-life photography?

但一些靜物照相又如何呢？

You can watch the ripples, again, washing over the table,

你可以看到波紋再次在桌子上展開，

the tomato and the wall in the back.

背景是紅番茄和牆。

It's like throwing a stone in a pond of water.

這就像在水池裏扔一塊石頭。

I thought: this is how nature paints a photo,

我想，這就是自然如何繪制的紅番茄，

one femto frame at a time,

一飛秒一飛秒，

but of course our eye sees an integral composite.

但當然我們眼睛看到的是整體的結合。

但如果你在看一下這個紅番茄，

But if you look at this tomato one more time,

you will notice, as the light washes over the tomato,

你就會注意到，當光在紅番茄上走過時，

它一直在閃耀。它並沒有變暗。

it continues to glow.

It doesn't become dark. Why is that?

爲什麽？因爲紅番茄熟了，

Because the tomato is actually ripe,

and the light is bouncing around inside the tomato,

並且光在紅番茄內部反射，

and it comes out after several trillionths of a second.

在幾萬億分之一秒後出來。

So in the future, when this femto-camera is in your camera phone,

所以，在未來，當飛米成像相機

在你的手機裏的時候，

you might be able to go to a supermarket

你就可以去超市，

and check if the fruit is ripe without actually touching it.

不用摸就能檢查一下水果是否熟了。

(Laughter)

那麽，麻省理工學院的團隊是怎麽做出這個相機的呢？

So how did my team at MIT create this camera?

現在，作爲攝影師，你知道，

Now, as photographers, you know,

如果你想要短時曝光，你只有一點點光，

if you take a short exposure photo, you get very little light.

但我們需要比最短的曝光時間

But we're going to go a billion times faster than your shortest exposure,

快一百萬倍，

so you're going to get hardly any light.

所以你幾乎得不到任何光。

So what we do is we send that bullet --

所以，我們做的是，

that packet of photons -- millions of times,

把這些光子送進去，並重複百萬多次，

and record again and again with very clever synchronization,

每次都以極好的同步錄像，

and from the gigabytes of data,

然後從數十億位元的數據中，

we computationally weave together

我們“編織”起來一幅圖，

to create those femto-videos I showed you.

而這幅圖就是你們之前看到的。

並且我們把所有的原始數據到算進去時，

And we can take all that raw data and treat it in very interesting ways.

進行很有趣的處理。

So, Superman can fly.

現在，超人能飛。

Some other heroes can become invisible.

一些其他英雄能隱身，

But what about a new power for a future superhero:

但想象一個未來的超人：

To see around corners.

他能看到拐角後面的東西。

The idea is that we could shine some light on the door,

這原理是我們可以把一些光打到門上，

it's going to bounce, go inside the room,

這些光會反射進入房間，

some of that is going to reflect back on the door,

一些會返回到門上，

and then back to the camera.

然後進入照相機，

And we could exploit these multiple bounces of light.

這樣我們就可以利用這些光的反射。

And it's not science fiction. We have actually built it.

這可不是科幻片。我們真正的做出來了。

On the left, you see our femto-camera.

在左邊，你看到了我們的飛秒成像相機。

There's a mannequin hidden behind a wall,

在牆後面有一個人體模型，

and we're going to bounce light off the door.

我們將進行光反射。

So after our paper was published in Nature Communications,

所以，在我們的論文發表

在《自然》上後，

it was highlighted by Nature.com,

它被推薦到自然的官網上，

and they created this animation.

然後他們創造了這個動畫。

(Music)

(音樂)

[A laser pulse is fired]

(Music)

我們將要發射這些光子彈，

Ramesh Raskar: We're going to fire those bullets of light,

and they're going to hit this wall,

它們將要撞擊這個牆，

and because of the packet of the photons,

並且因爲這束光

they will scatter in all the directions,

會散射到各個方向，

and some of them will reach our hidden mannequin,

一些會最終打到我們的隱藏的假人上，

which in turn will again scatter that light,

並且會繼續散射，

知道這個門也會反射

and again in turn, the door will reflect some of that scattered light.

一些光，

And a tiny fraction of the photons will actually come back to the camera,

而一部分光會最終

返回到相機裏，但最有趣的是，

but most interestingly,

they will all arrive at a slightly different time slot.

它們會在略微不同的時間到達。

(Music)

(音樂)

而且因爲我們有一個可以運行如此之快的相機，

And because we have a camera that can run so fast --

our femto-camera -- it has some unique abilities.

也就是我們的飛秒相機，這個相機就有一些特別的能力。

It has very good time resolution,

它有很好的時間分辨率，

and it can look at the world at the speed of light.

並且可以以光速捕捉世界。

And this way, we know the distances, of course to the door,

所以這樣，我們不僅知道相機到門的距離，

but also to the hidden objects,

同時知道到隱藏物品的距離，

but we don't know which point corresponds to which distance.

但我們不知道哪個點

對應哪個距離。

(Music)

(音樂)

By shining one laser, we can record one raw photo,

通過用激光，我們能記錄一個原始的照片，

which, if you look on the screen, doesn't really make any sense.

也就是你們在屏幕上看到的這個，好像沒什麽意義，

But then we will take a lot of such pictures,

但然後我們會拍很多照片，

很多很多，放到一起，

dozens of such pictures, put them together,

and try to analyze the multiple bounces of light,

然後分析光的反射，

and from that, can we see the hidden object?

現在我們能看到那個隱藏的物體了嗎？

Can we see it in full 3D?

我們能立體的看懂嗎？

So this is our reconstruction.

這就是我們的模型重建。 (音樂)

(Music)

(音樂)

(音樂) (掌聲)

(Applause)

現在距離我們在將這科技應用到生活中

Now, we have some ways to go

before we take this outside the lab on the road,

還有一些路要走，

but in the future, we could create cars that avoid collisions

但在未來，我們可以把這個技術放到車裏，

with what's around the bend.

這樣車就能防止碰撞，因爲他們能看到拐角，

Or we can look for survivors in hazardous conditions

或者我們可以搜尋幸存者，

by looking at light reflected through open windows.

因爲我們能看到在窗戶上反射的光，

Or we can build endoscopes that can see deep inside the body around occluders,

或者我們可以建造透視儀，

來看到身體裏的情況，

and also for cardioscopes.

我們甚至可以透視心臟。

But of course, because of tissue and blood,

但當然，由於各種組織和血液的幹擾，

this is quite challenging,

這回相當困難，

so this is really a call for scientists

所以我們呼籲科學家來真正重視飛秒成像，

to start thinking about femto-photography

as really a new imaging modality

把這個技術作爲一種

to solve the next generation of health-imaging problems.

解決下一代健康問題的新模型。

Now, like Doc Edgerton, a scientist himself,

現在，就像Edgerton博士，一個科學家，

science became art --

科學變成了藝術，一種高速攝影藝術，

an art of ultra-fast photography.

而且我意識到我們每次

And I realized

that all the gigabytes of data that we're collecting every time,

大量資料

are not just for scientific imaging.

不僅是科學成像，

But we can also do a new form of computational photography,

而是一種新的計算性攝影，

with time-lapse and color coding.

這種技術蘊含了時間延遲和彩色編碼，

And we look at those ripples.

我們看這些波紋。

Remember:

記住，這些波紋之間的時間

The time between each of those ripples is only a few trillionths of a second.

僅僅是幾個萬億分之一秒。

But there's also something funny going on here.

但有些有趣的事正在發生，

當你看到這些蓋子下的波紋時，

When you look at the ripples under the cap,

the ripples are moving away from us.

他們正在離我們遠去。

但這些波紋應該向我們移動。

The ripples should be moving towards us.

What's going on here?

發生了什麽？

It turns out, because we're recording nearly at the speed of light,

結果是，因爲我們在以接近光速

來錄這些東西，

we have strange effects,

我們有一些奇怪的現象，

and Einstein would have loved to see this picture.

愛因斯坦會相當高興看到這些圖片。

(Laughter)

The order at which events take place in the world

事件發生的順序

appears in the camera sometimes in reversed order.

在相機裏有時候被反轉了，

So by applying the corresponding space and time warp,

所以通過對應時間和空間的扭曲，

we can correct for this distortion.

我們可以修正這個扭曲。

So whether it's for photography around corners,

所以不管是看到拐角，

還是爲下一代製造健康影像，

or creating the next generation of health imaging,

or creating new visualizations,

還是增加新的可視化，

自從我們的發明，

since our invention,

we have open-sourced all the data and details on our website,

我們就已經把所有的資料和細節放到了我們的網上，

and our hope is that the DIY, the creative and the research communities

並且我們希望，這個DIY，這個創意的研究團體，

will show us that we should stop obsessing about the megapixels in cameras --

可以告訴我們

我們不應該再迷上高像素 —(笑聲)—

(Laughter)

and start focusing on the next dimension in imaging.

而開始關注成像技術的另一個維度。

It's about time.

時間差不多了。謝謝。 (掌聲)

Thank you.

(Applause)

(掌聲)