Every single one of us will lose or has already lost something we rely on every single day.
我们每个人都将会失去，或者已经失去我们每天依赖的事物。
I am of course talking about our keys.
当然，我是指我们的钥匙。
Just kidding. What I actually want to talk about is one of our most important senses: vision.
说笑的。其实，我想讨论的是我们最重要的感官：视力。
Every single day we each lose a little bit of our ability to refocus our eyes until we can't refocus at all.
每天，我们的眼睛都会失去一点点对焦的能力，直到我们完全无法对焦。
We call this condition presbyopia, and it affects two billion people worldwide. That's right, I said billion.
我们把这个症状称为老花眼，它影响着全球二十亿人。对的，我说的是亿。
If you haven't heard of presbyopia, and you're wondering, "Where are these two billion people?" here's a hint before I get into the details.
如果你从未听过老花眼，而且很疑惑，“这二十亿人在哪？”在我开始详细介绍之前，先简单解释一下。
It's the reason why people wear reading glasses or bifocal lenses.
老花眼是人们使用老花镜或双焦镜的原因。
I'll get started by describing the loss in refocusing ability leading up to presbyopia.
首先我会讲解失去对焦能力是怎么导致老花眼的。
As a newborn, you would have been able to focus as close as six and a half centimeters, if you wished to.
在新生儿时期，你的眼睛具有接近6.5公分的对焦能力，这是最好的情况。
By your mid-20s, you have about half of that focusing power left.
在二十多岁的时候，你只剩下一半的对焦能力。
10 centimeters or so, but close enough that you never notice the difference.
剩下大概10公分，但是你不会发现跟之前有什么差别。
By your late 40s though, the closest you can focus is about 25 centimeters, maybe even farther.
当你四十多岁的时候，你最多只能对焦大概25公分，甚至更远。
Losses in focusing ability beyond this point start affecting near-vision tasks like reading,
在那之后，失去的对焦能力会开始影响近距离的活动，例如阅读。
and by the time you reach age 60, nothing within a meter radius of you is clear.
当你60岁时，半径一米范围内的目标都会变得模糊不清。
Right now some of you are probably thinking, that sounds bad
现在，在座有人也许在想，虽然那听起来很糟糕，
but he means you in a figurative sense, only for the people that actually end up with presbyopia.
但“你”这个词只是代指那些真正患上老花眼的人们。
But no, when I say you, I literally mean that every single one of you will someday be presbyopic if you aren't already. That sounds a bit troubling.
不是的，当我说“你”的时候，我确实是指你们每一个人，如果没准备好，总有一天会患上老花眼。听起来很令人不安。
I want to remind you that presbyopia has been with us for all of human history and we've done a lot of different things to try and fix it.
我想提醒各位的是，老花眼贯穿了人类的历史，我们尝试过不同的方法来解决它。
So to start, let's imagine that you're sitting at a desk, reading.
首先，想象自己正坐在桌旁读报纸。
If you were presbyopic, it might look a little something like this.
如果你有老花眼，眼前就会是这样一番景象。
Anything close by, like the magazine, will be blurry.
任何附近的目标，例如杂志，会很模糊。
Moving on to solutions. First, reading glasses.
不过我们有解决方法。一、老花镜。
These have lenses with a single focal power tuned so that near objects come into focus.
它的镜片调整了单一聚焦力，让你可以对焦附近的目标。
But far objects necessarily go out of focus, meaning you have to constantly switch back and forth between wearing and not wearing them.
但是对于较远的目标则无法对焦，这意味着你需要一直在戴眼镜和不戴眼镜之间不停切换。
To solve this problem Benjamin Franklin invented what he called "double spectacles."
为了解决这个问题，本杰明·富兰克林发明了“双重眼镜”，也就是现在的双焦镜。
Today we call those bifocals, and what they let him do was see far when he looked up and see near when he looked down.
双焦镜可以帮助他透过镜片的上半部分看清远处，透过镜片的下半部分看清近处。
Today we also have progressive lenses which get rid of the line by smoothly varying the focal power from top to bottom.
今天，我们还有渐进镜片，可以把那条分隔线去掉，让聚焦力平滑地上下渐变。
The downside to both of these is that you lose field of vision at any given distance, because it gets split up from top to bottom like this.
这些镜片的缺点是，无论在哪个距离，你都会失去一部分视野，因为聚焦范围是上下分开的。
To see why that's a problem, imagine that you're climbing down a ladder or stairs.
为什么这依然是一个问题呢，想象你正在沿着梯子或楼梯向下走。
You look down to get your footing but it's blurry. Why would it be blurry?
你向下看，发现落脚点是模糊的。为什么呢？
Well, you look down and that's the near part of the lens, but the next step was past arm's reach, which for your eyes counts as far.
因为你向下看时透过的是镜片用来看近处的部分，但是你的下一步并非伸手可及，所以你的眼睛把它当成了远处的景象。
The next solution I want to point out is a little less common but comes up in contact lenses or LASIK surgeries, and it's called monovision.
下一个解决方法相对少见，但比较常见于隐形眼镜或激光手术，它叫单眼视。
It works by setting up the dominant eye to focus far and the other eye to focus near.
它把主眼用来对焦远处，另一只眼对焦近处。
Your brain does the work of intelligently putting together the sharpest parts from each eye's view,
你的大脑可以聪明地把每只眼最清晰的视觉部分结合在一起，
but the two eyes see slightly different things, and that makes it harder to judge distances binocularly.
但是，因为两只眼睛看见的事物略有不同，所以用双眼判断距离会比较困难。
So where does that leave us? We've come up with a lot of solutions but none of them quite restore natural refocusing.
那么，下一步怎么办呢？我们已经找到了许多解决方案，但是它们都不会帮助恢复自然的视力。
None of them let you just look at something and expect it to be in focus. But why?
它们没办法让你在观察任何事物时都能准确对焦。这是为什么呢？
Well, to explain that we'll want to take a look at the anatomy of the human eye.
在解释这个问题之前，我们需要简单了解一下人类眼睛的结构。
The part of the eye that allows us to refocus to different distances is called the crystalline lens.
眼睛的晶状体让我们能够在不同距离上对焦。
There are muscles surrounding the lens that can deform it into different shapes, which in turn changes its focusing power.
晶状体附近的肌肉可以通过改变它的形状来改变它的聚焦能力。

What happens when someone becomes presbyopic?
人类患上老花眼时会怎么样？
It turns out that the crystalline lens stiffens to the point that it doesn't really change shape anymore.
晶状体会硬化，导致无法再改变形状。
Now, thinking back on all the solutions I listed earlier,
现在，回想我之前列出的解决方案，
we can see that they all have something in common with the others but not with our eyes, and that is that they're all static.
它们都有共同之处，但是都和我们眼睛的构造不同，因为它们都是静止的。
It's like the optical equivalent of a pirate with a peg leg.
就像是装了义腿的海盗。
What is the optical equivalent of a modern prosthetic leg?
那什么是视觉中的义腿呢？
The last several decades have seen the creation and rapid development of what are called "focus-tunable lenses."
过去几十年间，“焦距可调镜片”技术获得了急速发展。
There are several different types. Mechanically-shifted Alvarez lenses, deformable liquid lenses and electronically-switched, liquid crystal lenses.
这种镜片有不同的种类。机械调节阿尔瓦雷斯镜片、可变形液态镜片和电子开关液晶镜片。
Now these have their own trade-offs, but what they don't skimp on is the visual experience.
它们都有自身的优点和局限性，但是都能够提供充足的视觉体验。
Full-field-of-view vision that can be sharp at any desired distance.
完整的视野，在任何距离范围内都很清晰。
OK, great. The lenses we need already exist. Problem solved, right? Not so fast.
很棒，我们已经有这些镜片了。问题解决了，对吗？没这么快。
Focus-tunable lenses add a bit of complexity to the equation.
焦距可调镜片增加了自身的复杂性。
The lenses don't have any way of knowing what distance they should be focused to.
这些镜片无法得知应该对焦于哪个距离。
What we need are glasses that, when you're looking far, far objects are sharp,
我们的眼镜需要做到，当你看远处，远的目标清晰，
and when you look near, near objects come into focus in your field of view, without you having to think about it.
当你看近处，近处的目标能够准确对焦，你甚至完全不会意识到这种转换。
What I've worked on these last few years at Stanford is building that exact intelligence around the lenses.
过去几年中，我一直在斯坦福从事这种智能镜片相关的研究。
Our prototype borrows technology from virtual and augmented reality systems to estimate focusing distance.
我们的原型利用了虚拟现实和增强现实技术来预测对焦的距离。
We have an eye tracker that can tell what direction our eyes are focused in.
这种装置内部有一个可以追踪眼睛对焦方向的追踪器。
Using two of these, we can triangulate your gaze direction to get a focus estimate.
使用这两种技术，我们可以把你的注视点三角化，从而预测对焦。
Just in case though, to increase reliability, we also added a distance sensor.
以防万一，为了增加可靠性，我们也增加了距离传感器。
The sensor is a camera that looks out at the world and reports distances to objects.
这是一个相机，看向外侧，并汇报与目标之间的距离。
We can again use your gaze direction to get a distance estimate for a second time.
然后，我们可以使用你的注视点再次预测距离。
We then fuse those two distance estimates and update the focus-tunable lens power accordingly.
接着，我们会融合这两个距离预测数据，对焦距可调镜片进行相应的调整更新。
The next step for us was to test our device on actual people.
下一步，我们需要让人们测试装置。
So we recruited about 100 presbyopes and had them test our device while we measured their performance.
我们找来了大约100名老花眼患者，让他们测试我们的装置，然后测量他们的表现。
What we saw convinced us right then that autofocals were the future.
结果使我们对自动聚焦镜的前景信心倍增。
Our participants could see more clearly, they could focus more quickly
参与者可以看得更清楚、对焦更快，
and they thought it was an easier and better focusing experience than their current correction.
他们认为比起目前的矫正方法，我们的装置能够更准确、更容易的对焦。
To put it simply, when it comes to vision, autofocals don't compromise like static corrections in use today do.
简单来说，对于视力，相比当今的静止矫正方法，自动聚焦镜不需要牺牲任何功能。
But I don't want to get ahead of myself. There's a lot of work for my colleagues and me left to do.
但我不想过于激进。我和同事还需要处理许多事项。
For example, our glasses are a bit -- bulky, maybe?
比如说，我们的眼镜有点笨重，也许吧？
And one reason for this is that we used bulkier components that are often intended for research use or industrial use.
一个原因就是，我们使用了研究和工业领域比较常用的更笨重的零件。
Another is that we need to strap everything down because current eye-tracking algorithms don't have the robustness that we need.
另外，我们还需要把全部部件整合在一起，因为目前的目光测量算法远不如我们预想的稳定。
So moving forward, as we move from a research setting into a start-up,
所以，下一步，当我们把这项技术从研究项目转变成初创公司时，
we plan to make future autofocals eventually look a little bit more like normal glasses.
我们打算把将来的自动对焦镜做得更像正常的眼镜。
For this to happen, we'll need to significantly improve the robustness of our eye-tracking solution.
为了达到这个目的，我们需要在更大程度上改进目光测量算法的稳定性。
We'll also need to incorporate smaller and more efficient electronics and lenses.
我们也需要加入更小、更高效的电子零件和镜片。
That said, even with our current prototype,
也就是说，即使处在原型阶段，
we've shown that today's focus-tunable lens technology is capable of outperforming traditional forms of static correction.
当前的焦距可调镜片科技也比传统静止矫正工具更加出色。
So it's only a matter of time.
一切只是时间问题。
It's pretty clear that in the near future, instead of worrying about which pair of glasses to use and when,
很明显，在不远的将来，我们不再需要纠结什么时候用什么眼镜，
we'll be able to just focus on the important things. Thank you.
而是可以专注于更重要的东西，谢谢。