Bill takes apart an LCD monitor and shows how it works. He explains how it uses liquid crystals, thin film transistors and polarizers to display information. EngineerGuy's new book is at www.engineerguy.com/elements.
+Immortal Okay so you know how light is a wave? Well that wave can go up and down(vertical), side to side(horizontal), or in between. Polarizing means to only allow light going in a specific direction. So if it's polarized for vertical light, all vertical waves go through, all horizontal light gets blocked, and in between waves kind of get through but are forced to become vertical. In an LCD screen, there's two polarizers, one for vertical, and another for horizontal. Light goes through the vertical polarizer --> all light is now vertical. But wait, when it hits the horizontal polarizer, none of the light will go through, right? Horizontal only lets through horizontal light, and we've just made all the light vertical. So between the two polarizers they place a sheet of liquid crystal. The liquid crystal can twist the light based on how it's warped, and you can warp the liquid crystal with electricity! (How that works is very complicated, that's where the real science and tech is). If you want light to go through, you apply an electric field to the liquid crystal, the liquid crystal warps, and the liquid crystal twists the light, making the vertical waves horizontal, thereby allowing it to pass through the horizontal polarizer. Then it hits the pixels and that's what you see on your screen.
+Immortal The essential element is light polarization, which isn't normally perceptible to our eyes. Light can contain a mixture of random polarization, or just one particular angle. It's like a straight-slot screw, and can be turned to any angle. There are filters that only let light with a certain polarization through, and block that which is at any different angle. Finally, via electrical control, the liquid crystal material can be made to either leave the polarization alone, or rotate it. Put these together and you get a light shutter that is electrically controlled: put a filter to allow only one polarization through, then the liquid crystal, and another filter that's rotated 90 degrees. When the liquid crystal is leaving polarization alone, you get dark because the front filter blocks the light with the wrong polarization. When it rotates polarization by 90 degrees, you get light because it goes through both filters.
More people than can be listed, depending on how you want to consider it. Think of how many prior discoveries the LCD panel relies upon, and how many prior discoveries those prior discoveries relied upon, and so on until the first invention.
The University of Hull, UK claim to have invented the LCD. They never bothered to patent it though because they thought it wouldn't be profitable... yeah, 'geniuses'...
The cool thing is that even newer displays are simpler. OLED's don't need backlight because it's the pixels themselves that emit a light, instead of just filtering the existing backlight. This means you don't need all the diffusing and polarising films, just the sheet of pixels. It also means you can turn pixels off to create perfect black and that it can be made to be even thinner, almost as thin as a piece of paper.
Actually it is not quite fair to say that OLEDs are simpler in functionality comparing to LCDs. Having fewer steps in sending the information to the end user does not necessarily mean that it is less complex. The sole technology behind the research and development of organic LEDs (OLEDs) is way more complex than filtering the white light as is in LCDs. I would compare OLEDs with CRTs in complexity, yet not with LCDs. Tough there are astonishing technologies used in LCDs both optical and physical.
I know this is old but this is what i was thinking about through the whole video. Why dont you just use pixels to create an image if yo are already giving the power to light up?
I have a Radio-Electronics magazine from April 1968, and there is a little article about RCA's liquid crystal display. It was monochromatic, and very small, perhaps 2 inches by 2 inches. Who knew the wide ranging result of that technology?
This video just amazes. I can't count how many times I have watched this video over the past three years. I have used this as a source of many projects throughout my college career. I have had to write technical papers, do expertise/explanation speeches for classes, and I always refer back to this video. It's so interesting, enjoyable, and easy to follow. Thank you, and I really hope more of these can be done someday.
This video made me understand and appreciate this technology in a way I never have before! Just kidding, what it really did was make me feel like an idiot.
In true OLEDs, every pixel is made of an organic light emitting diode which is controlled by a transistor (usually TFT as also used in LCD control) meaning if the transistor is on, then the OLED material emits light. Normally each OLED pixel can emit visible light of different colors(according to its production process it has a certain color gamut), emitting different colors at different voltages applied by TFT. By this way, pictures are produced. So, there is no backlight used in OLED displays, each OLED pixel emits its own light. It is similar to inorganic LEDs, when you apply a potential across the OLED, it shines light. But, as I am informed, most of the OLED panels produced in todays world are configured differently. In such configurations, OLED pixels do not emit different colors but produce just bright white light, and they use RGB filters on these OLED pixels in which these filters filter out red,green and blue lights creating sub pixels each paired with an OLED pixel. Thus, most OLED displays used today are not true OLED displays. Tough they are still more efficient, and have better contrast comparing to LCDs.
WOW!!!!!! THANK YOU, YOUR THE FIRST GUY TO BREAK IT DOWN WITH SUCH TALENT! FINALLY, A CLEAR BREAKDOWN OF HOW EACH PIXEL IS ACTIVATED!!! THANKS ENGINEER GUY!!!
Bill, I really appreciate your videos. There's more to be learned from another articulate human being than reading text. Keep up the good work and release more videos. I look forward to them.
Wow. All the hard work and brilliance that went into the creation of this technological wonder. All so that the world can watch Real House wives and the Kardashians. Do I laugh or cry?
I always knew about the RGB pixels and liquid crystal stuff. But I never fully understood how the rows are individually controlled. Didn't know there were tiny transistors either. Thanks for this insightful video!
Ive tried to understand this for a long time and watched several different videos but i finally was able to follow along and understand ( understand better than before ) well done sir
Oscar v Would be cool to see. I think there might be an issue with the frame rate pf the camera versus the refresh rate of the LCD in order to show it happen. Not sure.
Travis Wilson It's a heterodyning or stroboscopic effect due to differences in scanning rates. It's why looking at mags wheels of a moving car through a palisade fence makes the wheels appear to stationary or even rotate backwards. Same reason why the wagon wheels in old Westerns shot at less than 30fps appear to stop/rotate backwards when digitized at high modern rates.
Incredible video. Most would have just do it the ppt way. This is the channel that profound me as it have such a large subscriber base yet have no profit motivation (no sponsored product, no cheeky transition to some promotion etc) and stick true to just educating us, thumbs up!
Sypran if i'm not mistaken LED screen is the opposite of LCD. it uses sooo many tiny LEDs to light up each sub-pixel, so it consumes less energy when displaying black/dark images
Taufik Akbar There are those kinds of screens, but they are not used for TVs or Computer monitors. I believe the Times Square Coke sign uses that kind of display. LED TVs are exactly like what Bill showed in the video. They are technically LED LCDs, and the big difference is that it uses LEDs instead of a florescent tube for back lighting. OLED I am not 100% sure how it works but it requires no back light making it lighter, thinner, and consume less electricity. No light is emitted when a pixel is absolute black. I believe one of the Zunes used an OLED screen and that is why all it's menus were white text on a black background.
Taufik Akbar That would be quite difficult and expensive to produce. Each LED for a 24" 1920x1080 screen would be 0.0828mm. They all need to be uniformly bright, all 6,220,800 of them. There are too many "joints" or parts that can go wrong, specially since LEDs are not the most refined technology at the moment. The Back light of an LCD is were most of the power inefficiency comes from, not the LCD screen it's self. In fact LCDs tend to draw not nearly as much power as a the LEDs that light them. Odd fact that sorta has to do with the subject: A Nintendo DS doesn't work unless it detects a certain amount of electrical resistance to it's top screen. It only cares though about the electricity to power the LCD not the back light. The amount of resistance from what I recall is about equal to the little power light.
i have disassembled a lot of CRTs before like 25 CRTs and im 17 old i started when i was 9 i just liked the way you explained the porocess of the functioning unit it's ok THANK YOU GOD BLESS YOU sincerely Nikolay Veloz
+leelyana Ofcourse you arent stupid, dont be silly. The fact that you watched this video shows you are interested in finding out how stuff works, that on itself is a smart move. :)
The thing is, these days we are standing on the shoulders of generations of testing and innovation. No one person knows all the answers, but together over the centuries we have learnt what we have learnt. All the people involved in this innovation will have had to pool their technical knowledge to get the final result.
Thank you to the entire team of people that do these videos. I post on this one because it is my favorite, and I have even wrote several papers citing this video. Anyways, the team of people are so amazing at doing this. They are so amazing at how they are put together. I have learned so much from these videos and watch them all over and over again. They are so great in the sense that they are so easy for a person to follow. Also how a young person like myself can like it so much. Good Job guys!
Brilliant, I have tried to understand this for 20yrs and no one could tell me ! Why.......they obviously dont know, precisely, themselves........thanks soooo much !!!!
I love Bill's videos. All of them. I would like to point out that at that in general, what we see as "modern" technological advances generally have a long history behind them that build on hundreds of years of scientific research. The scientific research input that went into the LCD display could (in part) be traced back to the 1800's when scientists were figuring out what exactly electricity was and how it worked. There were some flaming rows about that in Italy between Volta and Galvani. The BBC makes good documentaries on such history. Understanding the nature of light and how it can be polarized also goes back to that time in history. As each branch of the sciences makes discoveries and advances and pass that knowledge onto engineers everyone involved builds of work of those that have gone before and pass their work on to the next generation. This is why for a lot of modern technological devices such as PCs, LCD screens and hard drives we do not associate them with a single inventor. Science and engineering is a team game, a game that we seem to have only really started to get very good at over the past few decades but it is a game that we been playing for much longer than that. en.wikipedia.org/wiki/History_of_display_technology
I always wondered how LCD screens work. And now I have a clear answer from an expert. Thank you Sir for such educational and inspiring videos. Your videos made me to love engg.
Thanks for making an excellent video ! You have a way of making something very complex much easier to understand. Even if one does not get the entire concept they will recieve a tremendous amount of knowledge to go forward with. Thanks again for taking the time to explain.
Respected Sir, Thanks a lot for this wonderful information. This video is an eye-opener for me. I never thought in my dreams that the there are transistors and polarisers for displaying information. God bless you.
I've wondered about how this worked exactly for years, and then you just explain it like it's the most simple thing in the world. Thanks, this really helped out!
FINALLY understood it. All of the other explanations I've seen couldn't make me grasp the full concept, but this one is just perfect. Would be interesting to have a little more detail on the material the first few sheets are made of (which evenly distribute LED light).
Nnnnnnnnice! Well explained. Always (until now) thought the LC makes the colours, but it actually "just" manages the light behind the pixelated TFT-layer.
I was cleaning out a LCD that got soaked in oil and needed to clean between the filters. I cleaned them in order and kept them stacked. However, I ended up dropping them and forgetting the right order. Thank you for making this video.
it is trully remarkable. I have no idea how they are manufacted so well that my 5-year old LCD screens work just as well as the day they were purchased
I've been using liquid crystal laminate ('tinted glass') to control the light in my study for about a decade and a half. The initial set up cost me a small fortune back in the day, but it was a novelty that I could apply to my entire home for less than a grand or two now, and power with a button cell recharged by a centimeter squared solar cell on the outside.
