The convention in science wasn't established and there were two major problems with red one.

科學界的公約並沒有建立起來，紅一有兩個主要問題。

There wasn't yet a way to make red pigment that wouldn't fade and to read is way harder to see.

當時還沒有一種方法可以使紅色顏料不褪色，而且要閱讀是很難看到的。

At night.

在晚上。

You see your eye has three types of cones that detect color red, green and blue cones.

你看你的眼睛有三種類型的錐體，檢測顏色的紅色、綠色和藍色錐體。

But at night there isn't enough light to activate these cones in your retina.

但在晚上，沒有足夠的光線來激活你視網膜上的這些錐體。

So your eyes rely on rods which are much better at perceiving low light.

所以你的眼睛依靠棒狀物，而棒狀物在感知弱光方面要好得多。

And if we look at the wavelength sensitivity of rods, you'll notice they actually don't even pick up red wavelengths when we see red at night, it can only be picked up by cones and as a result red is the hardest color to see in low light.

如果我們看一下桿狀體的波長敏感性，你會發現，當我們在晚上看到紅色時，它們實際上甚至不能接收紅色的波長，它只能被錐狀體所接收，是以，紅色是在弱光下最難看到的顏色。

So while a traffic light shining red is one thing a lowly lit red sign is completely different on top of this, even in daylight, our eyes are actual Most sensitive to a yellow greenish color.

是以，雖然交通信號燈閃耀的紅色是一回事，但低矮的紅色標誌是完全不同的，在此基礎上，即使在白天，我們的眼睛實際上對黃綠色最敏感。

This is because it's right in the overlap between our red and green cone sensitivity, peaking at about 550 nm making it a perfect option for visibility, but not exactly one for consistency with red meaning stop.

這是因為它正好處於我們的紅色和綠色錐體敏感度之間的重疊部分，在大約550納米處達到峰值，使其成為能見度的完美選擇，但不完全是一個與紅色意味著停止的一致性。

So when did the switch to red signs happen and how do we overcome this hurdle.

那麼，什麼時候改用紅色標誌的，我們如何克服這一障礙。

It's actually one of the most ingenious and coolest inventions to ever come about retro reflection.

它實際上是有史以來最巧妙和最酷的復古反射發明之一。

I'm here at three M.

我在這裡，在三M。

Innovation theater, the home of the retro reflector where it was invented, created and first implemented and we're gonna talk about what they are and how they work.

創新劇院，是復古反射器的故鄉，它是在那裡發明、創造和首次實施的，我們將討論它們是什麼，以及它們如何工作。

I have a little laser light here but to not blind you, we understand if a light comes into the mirror it's gonna reflect back into this lens or your eye.

我這裡有一個小小的激光燈，但為了不使你失明，我們知道如果有光進入鏡子，它會反射到這個鏡頭或你的眼睛。

But if you point a laser at an angle to a mirror it exits at the equal angle.

但如果你將脈衝光以一定的角度指向鏡子，它就會以相等的角度射出。

The other way you can see over there, I have that laser pointer on the shelf and that's not very useful if you're trying to get light reflecting back to someone on a sign.

另一種方式，你可以看到在那裡，我有那個激光指示器在架子上，如果你想讓光反射到標誌上的人身上，那就不是很有用。

So we need a better solution and three M.

所以我們需要一個更好的解決方案和三個M。

Came up with that many decades ago.

幾十年前就想到了這個辦法。

They first used these glass beads.

他們首先使用這些玻璃珠子。

Now when light enters glass is a different refractive index so it actually bends the light.

現在，當光線進入玻璃是一個不同的折射率，所以它實際上彎曲了光線。

We put this down here at the white surface that's reflective behind it.

我們把這個放在這裡，在它後面的白色表面上，是有反射的。

And I shine this laser through it.

而我用這種脈衝光照亮它。

You can see that laser comes back to me now instead of bouncing out the other direction, it's actually shooting back at my stomach a little faint but still there but three M.

你可以看到那道脈衝光現在回到了我身邊，而不是彈出了另一個方向，它實際上是射回了我的肚子，有點微弱，但仍然存在，但有三個M。

Took that principle even further with a full cube retro reflector if we take this and just talk about these first two mirrors here, if I shine a laser in one side of that mirror it will bounce out at the equal and opposite angle and then do it again and you can see on me this laser looks basically just as strong as it did going in as it does on me.

如果我們用一個全立方體的逆向反射鏡來進一步研究這個原理，只說說這裡的前兩個鏡子，如果我把脈衝光照到鏡子的一邊，它就會以相等和相反的角度反彈出來，然後再做一次，你可以看到這個脈衝光在我身上看起來基本上和它進去的時候一樣強烈。

So that's really useful that it's reflecting back to the source where it's coming from.

是以，這真的很有用，它可以反映出它的來源。

And when you think about signage, you want the light to hit it even if it's at a weird angle and come back to you.

而當你考慮到招牌時，你希望光線能照射到它，即使它的角度很奇怪，也能回到你身邊。

So you can see the thing by adding a third mirror down here.

所以你可以通過在下面添加第三面鏡子來看到這個東西。

We can now basically point anywhere on here and we're gonna have reflection that ends up back towards me.

我們現在基本上可以指向這裡的任何地方，我們會有反射，最後回到我的身邊。

You can see it here as well even though I'm pointing on the bottom and that is the basic 101 of how a retro reflector works.

你在這裡也可以看到，儘管我指的是底部，這就是複式反光鏡工作原理的基本101。

Now, the question is how do we go from the principle of retro reflection to getting it on a huge variety of surfaces, like not only signs, but multiple plastics.

現在，問題是我們如何從復古反射的原理到在大量的表面上得到它，比如不僅是標誌，還有多種塑膠。

The lines on the road and even clothing.

道路上的線條，甚至是衣服。

Walk me through what the heck you are moving around here, These are our reflective sheeting, What we have here.

讓我瞭解一下你在這裡移動的東西，這些是我們的反光板，我們這裡有什麼。

Different type of reflective sheeting.

不同類型的反光板。

So these are all basically full of retro reflectors correct.

是以，這些基本上都是充滿了復古的反射器正確。

This is full of retro reflectors.

這裡充滿了復古的反光鏡。

Basically each of these Little squares has 6000 retro factors per square centimeter.

基本上這些小方塊中的每一平方釐米都有6000個復古因素。

Yes, you did their homework.

是的，你做了他們的功課。

Pretty good.

相當不錯。

This though is like a metal backing of which these retro reflective sheets are put onto totally correct.

這雖然就像一個金屬背板，這些復古的反光板放在上面是完全正確的。

The most important sign of the stop signs with our materials.

最重要的標誌是用我們的材料做的停車標誌。

I wasn't about to leave without a sign of my own.

我不打算在沒有自己的標誌的情況下離開。

So I made sure to ask specifically how the signs get put to.

所以我一定要特別問一下，這些標誌是如何被放上去的。

We're gonna start with the retro reflective sheeting so we'll cut it to size And our retro reflective sheeting is basically a big sticker.

我們要從復古的反光板開始，所以我們要把它剪成合適的尺寸，我們的復古反光板基本上就是一張大的貼紙。

So there's a liner and adhesive on the back.

所以後面有一個襯墊和粘合劑。

So once you apply it on here, you get kind of this lip this overhang.

是以，一旦你把它塗在這裡，你就會得到這種脣部的這種懸空。

So we have to trim that off and then separately we'll take the electoral cut overlay film or some people call it and we'll put it through a friction fed plotter we wrote Science to keep this, we just kind of grab the edge and just push it and then you can just lift the letter off.

是以，我們必須將其修剪掉，然後分別將選舉過的覆蓋膜或一些人稱之為，我們將把它放在一個摩擦進給的繪圖儀上，我們寫了科學，以保持這個，我們只是一種抓住邊緣，只是推動它，然後你就可以把信提起來。

Oh you can't.

哦，你不能。

Okay, there we go.

好了，我們走吧。

Alright.

好吧。

Some letters like a will actually have a little floating piece right in the middle.

有些字母如a實際上會在正中間有一個小的浮動片。

And so applying this pre space allows you to keep everything in place and remove the liner essentially you end up with something like this.

是以，應用這個預留空間可以讓你保持所有的東西都在適當的位置，並移除襯墊，基本上你最終會得到這樣的東西。

So you remove the liner, the green is stuck to the white retro reflective sheeting.

所以你去掉襯墊，綠色被粘在白色的復古反光板上。

It's on aluminum.

這是在鋁上。

And the last thing to do is to remove this pre space which you want to give it.

而最後要做的是刪除這個你想給它的預留空間。

I would love to are we ready.

我很願意，我們準備好了嗎？

Oops, Wow, look at that Asap science.

Oops, Wow, 看看這個Asap科學。

Almost every street name sign is made like this before digital printing.

在數字印刷之前，幾乎每個街名標誌都是這樣做的。

That's crazy.

這很瘋狂。

And another way to manufacture science is using digital printing.

而另一種製造科學的方式是使用數字印刷。

So digital printing has been around for about 10.

是以，數字印刷已經存在了大約10年。

So this is printing on retro reflective sheeting.

所以這是在復古的反光板上印刷。

Exactly this specific printer uses HP latex inks.

確切地說，這種特定的打印機使用惠普乳膠油墨。

So it's water based.

所以它是水性的。

So it's similar to like your printer at home, we're just laying down all right, can we see a little something?

所以它類似於像你家裡的打印機一樣，我們只是躺下好了，我們能看到一點東西嗎？

Something?

什麼東西？

It's more a sub science science.

這更像是一門亞科學的科學。

That's so cool.

這真是太酷了。

Okay, we're outside in the dark and we're going to do a little experiment with the sign now to see it in action.

好了，我們在外面的黑暗中，我們現在要用這個標誌做一個小實驗，看看它的作用。

So, if I shine this flashlight on the ground, my immediate surroundings are pretty visible but become increasingly less visible as you go further out.

是以，如果我把這個手電筒照在地面上，我眼前的環境是相當明顯的，但隨著你越往外走，變得越來越不明顯。

And that's because light scatters in all directions and less photons are actually making it back to the camera lens.

這是因為光線向各個方向散射，真正能回到相機鏡頭的光子較少。

But if I shine this light now over towards Greg holding our fancy retro reflecting sign and put the light right beside the camera lens, you'll see just how much brighter the sign is than almost anything else the light is touching, even though it's all the way over there.

但是，如果我現在把這束光照向拿著我們花哨的復古反射標誌的格雷格，並把光放在相機鏡頭旁邊，你會看到標誌比光所接觸的其他東西要亮得多，儘管它一直在那裡。

Now, of course, if I move the light away from the lens, the sign becomes less bright.

現在，當然，如果我把光從鏡頭上移開，標誌就會變得不那麼明亮。

Even here, I'm about six inches go a little further about a foot, you can see how much darker the sign is and that's because the camera lens or you are no longer the source and instead the majority of the light is bouncing back over here.

即使在這裡，我大約六英寸，再往前走一點，大約一英尺，你可以看到標誌有多暗，這是因為相機鏡頭或你不再是光源，而是大部分的光線被反彈到這裡。

Over here, where I'm holding the light, I see the sun just as bright, but you don't and that's because the light is always reflecting back to the source.

在這裡，在我拿著燈的地方，我看到太陽一樣亮，但你沒有，這是因為光線總是反射到源頭。

You've likely seen this while driving at night when there are minimal overhead lights signs super far in the distance are extremely bright while things closer are completely dark, even the metal post seems invisible here.

你很可能在晚上開車時看到過這種情況，當頭頂上的燈光極少時，遠處的超級標誌非常明亮，而近處的東西則完全黑暗，甚至連金屬柱在這裡都似乎看不見。

Now.

現在。

What about when it's raining outside?

外面下雨的時候怎麼辦？

Sure, in the broad daylight you can still see the lines on the road.

當然，在光天化日之下，你仍然可以看到道路上的線條。

But I think we're all familiar with that scary problem of lines disappearing at night.

但我想我們都熟悉那個可怕的問題，即線條在夜間消失。

The problem here is that the water actually changes the refraction of light.

這裡的問題是，水實際上改變了光的折射。

So where the retro reflectors act ideally under dry conditions as soon as water is on top of them, their refractive index is lowered by a ratio of 1.33 and so the light leaves at a different angle sending less back to the source.

是以，在乾燥條件下，復古反射器的作用是理想的，只要水在它們上面，它們的折射率就會降低1.33的比例，是以光線以不同的角度離開，送回光源的數量就會減少。

And this is incredibly important because while only 25% of driving occurs at night, 55% of deaths from car accidents happen when it's dark with rain being disk proportionately dangerous at low light conditions compared to the day to combat this rain visibility problem three M actually developed these elements which are retro reflectors that have different refractive indices.

這一點非常重要，因為雖然只有25%的駕駛是在夜間進行的，但55%的車禍死亡是在黑暗中發生的，與白天相比，雨天在低光照條件下的危險性更高，為了解決雨天的能見度問題，三家公司實際上開發了這些元素，它們是具有不同折射率的逆向反射器。

So on this side we have elements that have a refractive index of 1.9 and they work well in dry conditions and on this side we have elements that have a 2.4 refractive index and work better in wet conditions and on top they're both in air and on the bottom they're both submerged in water.

是以，在這一側，我們有折射率為1.9的元素，它們在乾燥條件下工作良好，而在這一側，我們有折射率為2.4的元素，在潮溼條件下工作更好，在上面它們都在空氣中，在下面它們都浸泡在水中。

And I'm gonna show you what happens when we're in the dark and shine a light on both of these.

而我要告訴你當我們在黑暗中會發生什麼，並照亮這兩件事。

You can see that the one on the left at the top is optimized for dry conditions because it's flashing back more light and then the one at the bottom on the right is optimized for water and is sending more light back to us even though it's submerged in water.

你可以看到，頂部左邊的那個是為乾燥條件而優化的，因為它閃回更多的光，然後右邊底部的那個是為水而優化的，即使它浸泡在水中，也會向我們發出更多的光。

And of course the best solution is to include a mix of these elements in the product, whether it's the layer put on top of painted lines or directly into taped lines so that people can see them in either weather condition.

當然，最好的解決方案是在產品中包括這些元素的混合，無論是放在畫好的線條上的那一層，還是直接放在貼好的線條上，這樣人們在任何天氣條件下都能看到它們。

If it's dry, the one 0.9 will send the light back while the 2.4 won't.

如果它是乾的，一個0.9的會把光送回去，而2.4的則不會。

And when it's wet, the opposite occurs.

而當它潮溼時，就會出現相反的情況。

So behind me we have a variety of painted lines.

所以在我身後，我們有各種各樣的畫線。

Some have the regular glass beads on them and other ones have the three M.

有些上面有普通的玻璃珠，其他的則有三個M。

Elements on them with the 1.9 refractive index for the 2.4 refractive index or a combination of those and we're gonna see what happens in the dark when they get rained on here's the setup in the dark before the rain machine has been turned on and you can see all the lines are equally visible.

在他們身上的元素有1.9的折射率和2.4的折射率或這些元素的組合，我們要看看他們在黑暗中被雨淋後會發生什麼，這是雨淋機開啟前在黑暗中的設置，你可以看到所有的線條都是同樣可見的。

But as the rain begins to run, some of the lines slowly start to become obscured and harder and harder to see.

但隨著雨水開始流淌，一些線條慢慢開始變得模糊不清，越來越難看。

It's only the few stripes on this right hand side that remain visible as they have varying amounts of the water reflective elements.

只有這右側的幾條條紋仍然可見，因為它們有不同數量的水反射元素。

And here's the difference in the real world.

而這就是現實世界中的差異。

On the left is a wet line without water reflective elements.

左邊是一條沒有水反射元素的溼線。

And on the right you can see it with these elements and as a result you can actually see that line even in the rain.

而在右邊，你可以看到它與這些元素，結果你可以真正看到那條線，甚至在雨中。

So there you have it.

是以，你有了它。

Road signs are officially way cooler than you probably or at least are a lot cooler than I ever realized they were before making this video and hopefully I've convinced you of that too.

路標正式比你可能更酷，或者至少比我在製作這個視頻之前意識到的要酷得多，希望我也能讓你相信這一點。

I want to send a huge thank you for having me at the facility and to JC and gus for showing me around and teaching me and especially making me multiple signs that I can bring home back here to the ASAP science headquarters.

我想向你們致以深深的謝意，感謝你們讓我來到這個設施，感謝JC和Gus帶我參觀，教我，特別是讓我做了多個標誌，我可以把這些標誌帶回ASAP科學總部這裡。

I will cherish it forever.

我將永遠珍惜它。

Thank you so much for watching.

非常感謝您的觀看。

Make sure you like the video.

請確保你喜歡這段視頻。