Imaging at a trillion frames per second | Ramesh Raskar

Translator: Joseph Geni Reviewer: Thu-Huong Ha

翻译人员: Yilun Zhou 校对人员: Zhangyi Liu

Doc Edgerton inspired us with awe and curiosity

爱哲顿博士用这张子弹击穿苹果的照片

with this photo of a bullet piercing through an apple,

激起了我们的敬佩和好奇，

and exposure just a millionth of a second.

这张照片的曝光时间只有一百万分之一秒。

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

但现在，五十年后，我们可以再快一百万倍，

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

也就是不仅在一百万分之一秒，

或者十亿分之一秒，

but one trillion frames per second.

而是在万亿分之一秒见捕捉到世界。

现在我给你展示一种新型照相技术，

I present to you a new type of photography,

femto-photography,

叫做飞秒成像，

a new imaging technique so fast

这是一种技术太快以至于

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

它能捕捉到光的运动。

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

所以用这个技术，我们可以制造

能看到光路拐角的照相机，

beyond line of sight,

能看到视野之外

or see inside our body without an x-ray,

或者不用X光就能透视我们身体的照相机，

这种相机挑战了我们关于照相机的定义。

and really challenge what we mean by a camera.

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

现在，如果我用一个激光笔，

in one trillionth of a second --

并且在万亿分之一秒内开关一次——

which is several femtoseconds --

也就是几飞秒——

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

我就会制造一些光子，

这些光子仅仅是几毫米宽，

And that packet of photons, that bullet,

并且这些光子，像子弹一样，

will travel at the speed of light,

会以光速前进，

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

也就是比子弹速度高一百万倍。

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

现在，如果你把这个子弹，这些光子

and fire into this bottle,

打入这个瓶子里，

how will those photons shatter into this bottle?

这些光子会怎么样撞击瓶子？

How does light look in slow motion?

光在慢动作下会是什么样？

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

Now, the whole event --

现在，着整个事情—— （鼓掌）

(Applause)

（鼓掌）

Now remember, the whole event is effectively taking place

现在，请记住，这整个事情

其实是在一纳秒内发生的

in less than a nanosecond --

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

——也就是光走的时间——

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

但现在我再把这个录像放慢一百万倍

so you can see the light in motion.

让你看到运动中的光。

(Laughter)

But Coca-Cola did not sponsor this research.

但可口可乐可没有资助这个实验。 （笑声）

(Laughter)

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

现在，在这里有很多事会发生，

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

所以让我一件一件的展示。

So the pulse enters the bottle, our bullet,

现在，光束进入瓶子，也就是我们的子弹，

with a packet of photons that start traveling through

穿过瓶子，

and that start scattering inside.

并且在内部散射开来。

Some of the light leaks, goes on the table,

一些光流了出来，到了桌子上，

and you start seeing these ripples of waves.

所以你开始看到这些波纹。

Many of the photons eventually reach the cap

许多光子最终到达了瓶盖处

and then they explode in various directions.

并且向四周散去。

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

你能看到，这里是一个空气泡，

and it's bouncing around inside.

它在里面反弹。

Meanwhile, the ripples are traveling on the table,

同时，波纹也到了桌子上，

and because of the reflections at the top,

并且因为在顶部的反射，

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

你能看到在瓶子底部，几帧之后，

反射汇聚了。

the reflections are focused.

现在，如果你用普通的子弹

Now, if you take an ordinary bullet

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

走同样的路程，平且放慢视频，

again, by a factor of 10 billion --

同样是一百万倍，你知道

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

你需要等多久来看到这个全过程吗？

(Laughter)

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

一天，一周？实际上，是一年。

It'll be a very boring movie --

这当然会很无聊 （笑声）

(Laughter)

of a slow, ordinary bullet in motion.

一个慢的，普通的子弹运动录像。

And what about some still-life photography?

但一些静物照相又如何呢？

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

你可以又一次看到波纹在桌子上展开，

the tomato and the wall in the back.

背景是西红柿和墙。

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

这就像在水池里扔一块石头。

I thought: this is how nature paints a photo,

我想，这就是自然如何绘制的西红柿，

one femto frame at a time,

一飞秒一飞秒，

but of course our eye sees an integral composite.

但当然我们眼睛看到的是整体的结合。

但如果你在看一下这个西红柿，

But if you look at this tomato one more time,

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

你就会注意到，当光在西红柿上走过时，

它一直在闪耀。它并没有变暗。

it continues to glow.

It doesn't become dark. Why is that?

为什么？因为西红柿熟了，

Because the tomato is actually ripe,

and the light is bouncing around inside the tomato,

并且光在西红柿内部反射，

and it comes out after several trillionths of a second.

在几万亿分之一秒后出来。

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

所以，在未来，当飞米成像相机

在你的手机里的时候，

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.

不用摸就能检查一下水果是否熟了。

(Laughter)

那么，我在麻省理工学院的团队是怎么做出这个相机的呢？

So how did my team at MIT create this camera?

现在，作为摄影师，你知道，

Now, as photographers, you know,

如果你想要短时曝光，你只有一点点光，

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

但我们需要比最短的曝光时间

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

快一百万倍，

so you're going to get hardly any light.

所以你几乎得不到任何光。

So what we do is we send that bullet --

所以，我们做的是，

that packet of photons -- millions of times,

把这些光子送进去，并重复百万多次，

and record again and again with very clever synchronization,

每次都以极好的同步录像，

and from the gigabytes of data,

然后从几个GB的数据中，

we computationally weave together

我们“编织”起来一幅图，

to create those femto-videos I showed you.

而这幅图就是你们之前看到的。

并且我们把所有的原始数据到算进去时，

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

进行很有趣的处理。

So, Superman can fly.

现在，超人能飞。

Some other heroes can become invisible.

一些其他英雄能隐身，

But what about a new power for a future superhero:

但想象一个未来的超人：

To see around corners.

他能看到拐角后面的东西。

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

这原理是我们可以把一些光打到门上，

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

这些光会反射进入房间，

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

一些会返回到门上，

and then back to the camera.

然后进入照相机，

And we could exploit these multiple bounces of light.

这样我们就可以利用这些光的反射。

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

这可不是科幻片。我们真正的做出来了。

On the left, you see our femto-camera.

在左边，你看到了我们的飞秒成像相机。

There's a mannequin hidden behind a wall,

在墙后面有一个人体模型，

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

我们将进行光反射。

So after our paper was published in Nature Communications,

所以，在我们的论文发表

在《自然》上后，

it was highlighted by Nature.com,

它被推荐到自然的官网上，

and they created this animation.

然后他们创造了这个动画。

(Music)

（音乐）

[A laser pulse is fired]

(Music)

我们将要发射这些光子弹，

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

and they're going to hit this wall,

它们将要撞击这个墙，

and because of the packet of the photons,

并且因为这束光

they will scatter in all the directions,

会散射到各个方向，

and some of them will reach our hidden mannequin,

一些会最终打到我们的隐藏的假人上，

which in turn will again scatter that light,

并且会继续散射，

知道这个门也会反射

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,

而一部分光会最终

返回到相机里，但最有趣的是，

but most interestingly,

they will all arrive at a slightly different time slot.

他们会在略微不同的时间到达。

(Music)

（音乐）

而且因为我们有一个可以运行如此之快的相机，

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

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

也就是我们的飞秒相机，这个相机就有一些特别的能力。

It has very good time resolution,

它有很好的时间分辨率，

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

并且可以以光速捕捉世界。

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

所以这样，我们不仅知道相机到门的距离，

but also to the hidden objects,

同时知道到隐藏物品的距离，

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

但我们不知道哪个点

对应哪个距离。

(Music)

（音乐）

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

通过用激光，我们能记录一个原始的照片，

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

也就是你们在屏幕上看到的这个，好像没什么意义，

But then we will take a lot of such pictures,

但然后我们会拍很多照片，

很多很多，放到一起，

dozens of such pictures, put them together,

and try to analyze the multiple bounces of light,

然后分析光的反射，

and from that, can we see the hidden object?

现在我们能看到那个隐藏的物体了吗？

Can we see it in full 3D?

我们能立体的看懂吗？

So this is our reconstruction.

这就是我们的模型重建。 （音乐）

(Music)

（音乐）

（音乐） （掌声）

(Applause)

现在我们在把他们应用到生活中

Now, we have some ways to go

before we take this outside the lab on the road,

还有一些路要走，

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

但在未来，我们可以把这个技术放到车里，

with what's around the bend.

这样车就能防止碰撞，因为他们能看到拐角，

Or we can look for survivors in hazardous conditions

或者我们可以搜寻幸存者，

by looking at light reflected through open windows.

因为我们能看到在窗户上反射的光，

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

或者我们可以建造透视仪，

来看到身体里的情况，

and also for cardioscopes.

我们甚至可以透视心脏。

But of course, because of tissue and blood,

但当然，由于各种组织和血液的干扰，

this is quite challenging,

这回相当困难，

so this is really a call for scientists

所以我们呼吁科学家来真正重视飞秒成像，

to start thinking about femto-photography

as really a new imaging modality

把这个技术作为一种

to solve the next generation of health-imaging problems.

解决下一代健康问题的新模型。

Now, like Doc Edgerton, a scientist himself,

现在，就像爱哲顿博士，一个科学家，

science became art --

科学变成了艺术，一种高速摄影艺术，

an art of ultra-fast photography.

而且我意识到我们每次

And I realized

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

收集到的大量资料

are not just for scientific imaging.

不仅是科学成像，

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

而且还是一种新的计算性摄影，

with time-lapse and color coding.

这种技术蕴含了时间延迟和彩色编码，

And we look at those ripples.

我们看这些波纹。

Remember:

记住，这些波纹之间的时间

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

仅仅是几个万亿分之一秒。

But there's also something funny going on here.

但有些有趣的事正在发生，

当你看到这些盖子下的波纹时，

When you look at the ripples under the cap,

the ripples are moving away from us.

他们正在离我们远去。

但这些波纹应该向我们移动。

The ripples should be moving towards us.

What's going on here?

发生了什么？

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

结果是，因为我们在以接近光速

来录这些东西，

we have strange effects,

我们有一些奇怪的现象，

and Einstein would have loved to see this picture.

爱因斯坦会相当高兴看到这些图片。

(Laughter)

The order at which events take place in the world

事件发生的顺序

appears in the camera sometimes in reversed order.

在相机里有时候被反转了，

So by applying the corresponding space and time warp,

所以通过对应时间和空间的扭曲，

we can correct for this distortion.

我们可以修正这个扭曲。

So whether it's for photography around corners,

所以不管是看到拐角，

还是为下一代制造健康影像，

or creating the next generation of health imaging,

or creating new visualizations,

还是增加新的可视化，

自从我们的发明，

since our invention,

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

我们就已经把所有的资料和细节放到了我们的网上，

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

并且我们希望，这个DIY，这个创意的研究团体，

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

可以告诉我们

我们不应该再迷上高像素——（笑声）——

(Laughter)

and start focusing on the next dimension in imaging.

而开始关注成像技术的另一个维度。

It's about time.

时间差不多了。谢谢。 （掌声）

Thank you.

(Applause)

（掌声）