WEBVTT 00:00:00.902 --> 00:00:06.856 Doc Edgerton inspired us with awe and curiosity 00:00:06.880 --> 00:00:12.118 with this photo of a bullet piercing through an apple, 00:00:12.142 --> 00:00:15.994 and exposure just a millionth of a second. 00:00:17.661 --> 00:00:24.550 But now, 50 years later, we can go a million times faster 00:00:24.574 --> 00:00:29.336 and see the world not at a million or a billion, 00:00:29.360 --> 00:00:32.413 but one trillion frames per second. NOTE Paragraph 00:00:33.865 --> 00:00:37.529 I present to you a new type of photography, 00:00:37.553 --> 00:00:39.588 femto-photography, 00:00:39.612 --> 00:00:44.188 a new imaging technique so fast 00:00:44.212 --> 00:00:48.484 that it can create slow motion videos of light in motion. 00:00:49.413 --> 00:00:54.272 And with that, we can create cameras that can look around corners, 00:00:54.296 --> 00:00:56.269 beyond line of sight, 00:00:56.293 --> 00:01:01.149 or see inside our body without an x-ray, 00:01:01.173 --> 00:01:04.980 and really challenge what we mean by a camera. NOTE Paragraph 00:01:06.440 --> 00:01:09.574 Now if I take a laser pointer and turn it on and off 00:01:09.598 --> 00:01:12.401 in one trillionth of a second -- 00:01:12.425 --> 00:01:15.212 which is several femtoseconds -- 00:01:15.236 --> 00:01:19.233 I'll create a packet of photons barely a millimeter wide. 00:01:20.360 --> 00:01:22.769 And that packet of photons, that bullet, 00:01:22.793 --> 00:01:24.719 will travel at the speed of light, 00:01:24.743 --> 00:01:28.701 and again, a million times faster than an ordinary bullet. 00:01:29.622 --> 00:01:34.133 Now, if you take that bullet and take this packet of photons 00:01:34.157 --> 00:01:37.489 and fire into this bottle, 00:01:37.513 --> 00:01:41.084 how will those photons shatter into this bottle? 00:01:41.864 --> 00:01:44.452 How does light look in slow motion? NOTE Paragraph 00:01:44.552 --> 00:01:47.552 [Light in Slow Motion ... 10 Billion x Slow] NOTE Paragraph 00:02:06.041 --> 00:02:07.588 Now, the whole event -- NOTE Paragraph 00:02:07.612 --> 00:02:14.599 (Applause) NOTE Paragraph 00:02:14.623 --> 00:02:18.124 Now remember, the whole event is effectively taking place 00:02:18.148 --> 00:02:19.811 in less than a nanosecond -- 00:02:19.835 --> 00:02:22.236 that's how much time it takes for light to travel. 00:02:22.260 --> 00:02:26.907 But I'm slowing down in this video by a factor of 10 billion, 00:02:26.931 --> 00:02:29.479 so you can see the light in motion. NOTE Paragraph 00:02:29.503 --> 00:02:30.573 (Laughter) NOTE Paragraph 00:02:30.597 --> 00:02:32.884 But Coca-Cola did not sponsor this research. NOTE Paragraph 00:02:32.908 --> 00:02:35.010 (Laughter) NOTE Paragraph 00:02:35.034 --> 00:02:37.057 Now, there's a lot going on in this movie, 00:02:37.081 --> 00:02:39.701 so let me break this down and show you what's going on. 00:02:39.725 --> 00:02:42.659 So the pulse enters the bottle, our bullet, 00:02:42.683 --> 00:02:45.221 with a packet of photons that start traveling through 00:02:45.245 --> 00:02:47.058 and that start scattering inside. 00:02:47.082 --> 00:02:49.289 Some of the light leaks, goes on the table, 00:02:49.313 --> 00:02:51.925 and you start seeing these ripples of waves. 00:02:51.949 --> 00:02:54.957 Many of the photons eventually reach the cap 00:02:54.981 --> 00:02:57.871 and then they explode in various directions. 00:02:57.895 --> 00:02:59.783 As you can see, there's a bubble of air 00:02:59.807 --> 00:03:01.449 and it's bouncing around inside. 00:03:01.473 --> 00:03:03.923 Meanwhile, the ripples are traveling on the table, 00:03:03.947 --> 00:03:05.947 and because of the reflections at the top, 00:03:05.971 --> 00:03:09.718 you see at the back of the bottle, after several frames, 00:03:09.742 --> 00:03:11.441 the reflections are focused. NOTE Paragraph 00:03:13.210 --> 00:03:18.599 Now, if you take an ordinary bullet 00:03:18.623 --> 00:03:21.623 and let it go the same distance and slow down the video -- 00:03:21.647 --> 00:03:23.868 again, by a factor of 10 billion -- 00:03:23.892 --> 00:03:28.285 do you know how long you'll have to sit here to watch that movie? NOTE Paragraph 00:03:28.309 --> 00:03:29.897 (Laughter) NOTE Paragraph 00:03:29.921 --> 00:03:33.430 A day, a week? Actually, a whole year. 00:03:34.309 --> 00:03:36.566 It'll be a very boring movie -- NOTE Paragraph 00:03:36.590 --> 00:03:37.981 (Laughter) NOTE Paragraph 00:03:38.005 --> 00:03:41.377 of a slow, ordinary bullet in motion. NOTE Paragraph 00:03:42.700 --> 00:03:46.057 And what about some still-life photography? 00:03:53.112 --> 00:03:58.098 You can watch the ripples, again, washing over the table, 00:03:58.122 --> 00:04:00.780 the tomato and the wall in the back. 00:04:00.804 --> 00:04:03.594 It's like throwing a stone in a pond of water. NOTE Paragraph 00:04:07.403 --> 00:04:11.063 I thought: this is how nature paints a photo, 00:04:11.087 --> 00:04:13.650 one femto frame at a time, 00:04:13.674 --> 00:04:17.931 but of course our eye sees an integral composite. 00:04:19.923 --> 00:04:22.057 But if you look at this tomato one more time, 00:04:22.081 --> 00:04:24.826 you will notice, as the light washes over the tomato, 00:04:24.850 --> 00:04:26.514 it continues to glow. 00:04:26.538 --> 00:04:28.565 It doesn't become dark. Why is that? 00:04:28.589 --> 00:04:30.887 Because the tomato is actually ripe, 00:04:30.911 --> 00:04:33.300 and the light is bouncing around inside the tomato, 00:04:33.324 --> 00:04:36.744 and it comes out after several trillionths of a second. 00:04:37.714 --> 00:04:42.053 So in the future, when this femto-camera is in your camera phone, 00:04:42.077 --> 00:04:44.031 you might be able to go to a supermarket 00:04:44.055 --> 00:04:47.110 and check if the fruit is ripe without actually touching it. NOTE Paragraph 00:04:47.134 --> 00:04:48.820 (Laughter) NOTE Paragraph 00:04:48.844 --> 00:04:52.533 So how did my team at MIT create this camera? 00:04:53.906 --> 00:04:55.850 Now, as photographers, you know, 00:04:55.874 --> 00:04:59.835 if you take a short exposure photo, you get very little light. 00:04:59.859 --> 00:05:03.367 But we're going to go a billion times faster than your shortest exposure, 00:05:03.391 --> 00:05:05.320 so you're going to get hardly any light. 00:05:05.344 --> 00:05:07.257 So what we do is we send that bullet -- 00:05:07.281 --> 00:05:09.777 that packet of photons -- millions of times, 00:05:09.801 --> 00:05:12.884 and record again and again with very clever synchronization, 00:05:12.908 --> 00:05:14.847 and from the gigabytes of data, 00:05:14.871 --> 00:05:17.091 we computationally weave together 00:05:17.115 --> 00:05:20.014 to create those femto-videos I showed you. NOTE Paragraph 00:05:21.196 --> 00:05:25.346 And we can take all that raw data and treat it in very interesting ways. 00:05:26.015 --> 00:05:27.832 So, Superman can fly. 00:05:27.856 --> 00:05:30.114 Some other heroes can become invisible. 00:05:30.610 --> 00:05:35.392 But what about a new power for a future superhero: 00:05:35.416 --> 00:05:37.277 To see around corners. 00:05:38.094 --> 00:05:42.563 The idea is that we could shine some light on the door, 00:05:42.587 --> 00:05:45.238 it's going to bounce, go inside the room, 00:05:45.262 --> 00:05:47.668 some of that is going to reflect back on the door, 00:05:47.692 --> 00:05:49.175 and then back to the camera. 00:05:49.199 --> 00:05:52.196 And we could exploit these multiple bounces of light. NOTE Paragraph 00:05:52.687 --> 00:05:55.354 And it's not science fiction. We have actually built it. 00:05:55.378 --> 00:05:57.444 On the left, you see our femto-camera. 00:05:57.468 --> 00:05:59.823 There's a mannequin hidden behind a wall, 00:05:59.847 --> 00:06:02.352 and we're going to bounce light off the door. NOTE Paragraph 00:06:02.749 --> 00:06:06.242 So after our paper was published in Nature Communications, 00:06:06.266 --> 00:06:08.408 it was highlighted by Nature.com, 00:06:08.432 --> 00:06:10.908 and they created this animation. NOTE Paragraph 00:06:10.932 --> 00:06:12.216 (Music) NOTE Paragraph 00:06:12.240 --> 00:06:15.104 [A laser pulse is fired] NOTE Paragraph 00:06:15.128 --> 00:06:18.000 (Music) NOTE Paragraph 00:06:18.024 --> 00:06:20.891 Ramesh Raskar: We're going to fire those bullets of light, 00:06:20.915 --> 00:06:24.291 and they're going to hit this wall, 00:06:24.315 --> 00:06:26.946 and because of the packet of the photons, 00:06:26.970 --> 00:06:29.080 they will scatter in all the directions, 00:06:29.104 --> 00:06:31.445 and some of them will reach our hidden mannequin, 00:06:31.469 --> 00:06:34.851 which in turn will again scatter that light, 00:06:34.875 --> 00:06:39.446 and again in turn, the door will reflect some of that scattered light. 00:06:40.683 --> 00:06:44.179 And a tiny fraction of the photons will actually come back to the camera, 00:06:44.203 --> 00:06:45.354 but most interestingly, 00:06:45.378 --> 00:06:48.461 they will all arrive at a slightly different time slot. NOTE Paragraph 00:06:48.926 --> 00:06:53.759 (Music) NOTE Paragraph 00:06:53.783 --> 00:06:56.296 And because we have a camera that can run so fast -- 00:06:56.320 --> 00:06:59.402 our femto-camera -- it has some unique abilities. 00:06:59.426 --> 00:07:02.244 It has very good time resolution, 00:07:02.268 --> 00:07:05.163 and it can look at the world at the speed of light. 00:07:06.114 --> 00:07:09.371 And this way, we know the distances, of course to the door, 00:07:09.395 --> 00:07:11.172 but also to the hidden objects, 00:07:11.196 --> 00:07:14.353 but we don't know which point corresponds to which distance. NOTE Paragraph 00:07:14.377 --> 00:07:18.422 (Music) NOTE Paragraph 00:07:18.446 --> 00:07:21.876 By shining one laser, we can record one raw photo, 00:07:21.900 --> 00:07:24.924 which, if you look on the screen, doesn't really make any sense. 00:07:24.948 --> 00:07:27.068 But then we will take a lot of such pictures, 00:07:27.092 --> 00:07:29.252 dozens of such pictures, put them together, 00:07:29.276 --> 00:07:31.734 and try to analyze the multiple bounces of light, 00:07:31.758 --> 00:07:35.209 and from that, can we see the hidden object? 00:07:35.233 --> 00:07:37.367 Can we see it in full 3D? NOTE Paragraph 00:07:38.113 --> 00:07:40.042 So this is our reconstruction. NOTE Paragraph 00:07:40.066 --> 00:07:45.196 (Music) NOTE Paragraph 00:07:45.220 --> 00:07:52.196 (Applause) NOTE Paragraph 00:07:52.791 --> 00:07:54.260 Now, we have some ways to go 00:07:54.284 --> 00:07:57.419 before we take this outside the lab on the road, 00:07:57.443 --> 00:08:01.172 but in the future, we could create cars that avoid collisions 00:08:01.196 --> 00:08:02.677 with what's around the bend. 00:08:03.581 --> 00:08:07.668 Or we can look for survivors in hazardous conditions 00:08:07.692 --> 00:08:10.916 by looking at light reflected through open windows. 00:08:11.604 --> 00:08:17.475 Or we can build endoscopes that can see deep inside the body around occluders, 00:08:17.499 --> 00:08:19.199 and also for cardioscopes. 00:08:19.223 --> 00:08:21.589 But of course, because of tissue and blood, 00:08:21.613 --> 00:08:22.868 this is quite challenging, 00:08:22.892 --> 00:08:24.827 so this is really a call for scientists 00:08:24.851 --> 00:08:27.158 to start thinking about femto-photography 00:08:27.182 --> 00:08:29.063 as really a new imaging modality 00:08:29.087 --> 00:08:32.607 to solve the next generation of health-imaging problems. NOTE Paragraph 00:08:33.082 --> 00:08:36.939 Now, like Doc Edgerton, a scientist himself, 00:08:36.963 --> 00:08:39.266 science became art -- 00:08:39.290 --> 00:08:41.952 an art of ultra-fast photography. 00:08:42.880 --> 00:08:44.031 And I realized 00:08:44.055 --> 00:08:47.496 that all the gigabytes of data that we're collecting every time, 00:08:47.520 --> 00:08:49.941 are not just for scientific imaging. 00:08:49.965 --> 00:08:55.504 But we can also do a new form of computational photography, 00:08:55.528 --> 00:08:58.060 with time-lapse and color coding. 00:08:59.147 --> 00:09:00.616 And we look at those ripples. 00:09:00.640 --> 00:09:01.798 Remember: 00:09:01.822 --> 00:09:07.295 The time between each of those ripples is only a few trillionths of a second. NOTE Paragraph 00:09:08.602 --> 00:09:10.809 But there's also something funny going on here. 00:09:10.833 --> 00:09:13.629 When you look at the ripples under the cap, 00:09:13.653 --> 00:09:15.836 the ripples are moving away from us. 00:09:16.851 --> 00:09:18.765 The ripples should be moving towards us. 00:09:18.789 --> 00:09:20.161 What's going on here? NOTE Paragraph 00:09:20.185 --> 00:09:26.975 It turns out, because we're recording nearly at the speed of light, 00:09:26.999 --> 00:09:28.888 we have strange effects, 00:09:28.912 --> 00:09:32.173 and Einstein would have loved to see this picture. NOTE Paragraph 00:09:32.197 --> 00:09:33.236 (Laughter) NOTE Paragraph 00:09:33.260 --> 00:09:36.307 The order at which events take place in the world 00:09:36.331 --> 00:09:39.657 appears in the camera sometimes in reversed order. 00:09:41.046 --> 00:09:44.241 So by applying the corresponding space and time warp, 00:09:44.265 --> 00:09:46.632 we can correct for this distortion. NOTE Paragraph 00:09:48.606 --> 00:09:52.955 So whether it's for photography around corners, 00:09:52.979 --> 00:09:56.975 or creating the next generation of health imaging, 00:09:56.999 --> 00:09:59.891 or creating new visualizations, 00:09:59.915 --> 00:10:01.539 since our invention, 00:10:01.563 --> 00:10:06.688 we have open-sourced all the data and details on our website, 00:10:06.712 --> 00:10:13.665 and our hope is that the DIY, the creative and the research communities 00:10:13.689 --> 00:10:19.194 will show us that we should stop obsessing about the megapixels in cameras -- NOTE Paragraph 00:10:19.218 --> 00:10:20.497 (Laughter) NOTE Paragraph 00:10:20.521 --> 00:10:24.909 and start focusing on the next dimension in imaging. 00:10:25.607 --> 00:10:26.917 It's about time. NOTE Paragraph 00:10:27.337 --> 00:10:28.489 Thank you. NOTE Paragraph 00:10:28.513 --> 00:10:35.383 (Applause)