Before taking the subway, I've always wondered how the ads outside the window show up. Between them, it's been two years since I left this doubt in the WeChat collection. Today I finally found the right video to explain!
Tunnel lampposts First look at a Beijing subway show tunnel ads, sometimes there will be or fast or slow black line, there is a very prestabilizing sense of playback ... This.The display of the advertisement was fixed in the tunnel, not that any projectors were mounted on the windows outside the subway. I'll get through it first: The principle isThe following illustration shows a single column of LED lampposts, which areIn turn there is an interval after the row, giveInstallation.It's on the wall of the subway tunnelSo that as soon as the subway runs, you can see the advertisement on the wall through the window. But these are single columns of lampposts, how to "spell" into a clear picture? To explain the imaging of this tunnel advertisement, we start with the "visual residue" of the human eye - don't worry, it's not hard!
Visual residue Recall when I was a child, I very much love in the corner of the homework book page number to draw small people, and then quickly turn the small corner of the book, small people move up!This is because when you turn over a book,The previous picture is still in our mind, the 31 changed picture one after another, this has a coherent action, this is the visual residual phenomenon of the human eye.The image below is a demonstration device I photographed at the National Museum of Singapore, and it is also a visual residue... And China's earliest use of visual residue manufacturing device is probably a horse lamp. The appearance of the film also used this principle, we manageEach picture is called a frame, and the number of frames played per second is called the frame rate. The standard movie is 24 frames per second, which means that there are 24 consecutive images in a second. That.We now assume that the torch motion picture above is playing a normal movie, and you now just have to stare at one of the seats. Well, the speed of the table needs to turn through all the different shapes very quickly before you can see this coherent ignition action. LED walking lights
Now let's think about it in depth, you see, if it's all physical seats, we have to have 20 models of different movements, which is a lot of trouble, toHow can you save more time?What if you change the background to a simple lamppost, the only difference between flashing and not flashing?For example, if you want to display the number 5, each column is lit in a different position, and the combination is 5(Xiaojiang said: Take away my electric book!) )。As shown in the figure below, we only need to have a column of LED lamp posts in our hands, so that the flashing interval between the previous and last columns is less than 0.1s. But how can you tell from the naked eye? The brain will tell you that the positions of these 5 columns are still lit up, forming a complete number 5! In fact, the lampposts have long moved out of the picture, but you still feel as if you are watching the whole picture have lights flashing. If there is a little difficult to understand here, small cute think about when I was a child to play with the fireworks stick, dark night, clearly only the top of the fireworks in the fire light, but you shake hard, you see a whole bright line, this is also a visual residue - I read a time also popular with long exposure to shoot fireworks sticks or mobile phone bright screen to write what confession. Shake the light With this visual residual phenomenon, coupled with a single column of LED lamp posts, you can make a "shaking lamp" - this is also meIn college next door class to learn mechanical and electronic students, basically everyone has to do homework... Relying only on such a single column of LED lights, and then calculate the chassis rotation rate, and then to balance the light flashing frequency, it seems very stable display text.
Flash fan According to the principle of "shaking lights", what is the most popular commodity made? Is you on the street roadside, often sent by merchants with advertising text of the small fan... I also checked the next 1688, a large quantity of purchase prices stable at two pieces below five.
Subway tunnel ads So what does the principle of this thing have to do with subway tunnel advertising? Now you take a deep breath and calm down. You want to... When we went to see the whole "flash fan",It's our eyes that stay still. So if the lampposts don't move and the human eye is moving, isn't that what we're looking at in the subway tunnel ad? While taking the subway, our eyes follow the subway has been moving rapidly in one direction, and the LED lamppost is fixed in the tunnel, the human eye as a reference, that LED lamppost is moving, which will produce visual residue. What can you do to see the pattern clearly? It's still a single column of LED lampposts, moving toward us in the tunnel, fixed at different intervals, and flashing columns in turn. Now quickly simulate the speed of the subway, the human eye to follow the rapid movement up, you see a Picture of the Haier brothers.
Precise fit Single-column lampposts don't always blink. When a subway train approaches a lamppost, it receives a signal of the speed at which the subway is running, and then begins to adjust the flashing frequency through the established formula. In order to ensure good visual residue effect, the slower the subway speed, the faster the lamp post flashing frequency, in short, try to show you a stable display of the picture. Let's look at the tunnel ads in this subway, sometimes faster, sometimes slower, and even black, because of the accuracy problems caused by the failure of the subway speed and flashing frequency to fully align. Now a lot of relatively new urban subway, installed is the updated tunnel advertising system, generally there is no such problem.
Wait a minute! Cast has something to say This article demystification, a formula has not been put, all rely on examples... Shouldn't everyone understand? Wrote in milk cartons before the last discovery? Does the little color block above have any special meaning? There's also an introduction to visual residue... Ah haha, write too much sometimes I forget to write...My grandmother said that before in the street also encountered a small fan with advertising text, now can only lead one「Fan.」There are even fewer convenience stickers.
Proofreading: Cast and Jiang Xiaose
Screenshot: Yangge
Gif is taken from this article YouTube blogger Richz's "Beijing Subway cars have awesome advertisements in windows," the circuit's "C131 8 4A Shaking Lights Design Principles," 陳's 燁's "USB Flash Fan," Discovery's "Man Made Marvels" Beijing metro system, and I shot it at the National Museum of Singapore "Walking horses and flowers" principle point torch demonstration device
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