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Source: MovieWorldMap.com
From the opening of Universal Studios Beijing to the release of Harry Potter-related mobile games, to the magic of Halloween, this autumn has always been filled with a strong "magic" atmosphere.
More than 20 years after the release of the first harry potter series, Hogwarts is still glamorous. Most of the little wizards of that year have grown up, but they are still looking forward to finding the traces of the nine and three-quarters platform and entering the mysterious magical world through it. And at Universal Studios Orlando, people seem to have actually discovered its entrance.
Platform-through-wall magic: Tourists are pushing carts through walls. Source: TwoWayMirrors.com
There is some kind of "magic" principle behind this mythical image—but in our Muggle lingua franca, it's called science. It's a type of hallucination imaging called pepper's ghost. It's not complicated, but it's key to the famous holographic projection technology. To understand its origins, we need to go back to a time when it was really full of "black magic."
The more frightened you are, the more you want to see it — hundreds of years ago, all kinds of tricks, illusions and other mysterious performances have become an important pastime for people.
The prevailing view is that it was scientist Christiaan Huygens who formally invented the "magical lantern", the prototype of the slide projector through the combination of lenses to project the image on the picture to a certain location. The promotion and continuous improvement of magic lanterns brought the magic performances of the time to new heights.
Huygens is credited with being the scientist who developed the magic lamp earlier. One of his sketches shows the horror trick he demonstrated with a magic lamp— the process of taking his head off.
One of the most famous illusionists, also a scientist, Robertson (full name Étienne-Gaspard Robert, stage name Robertson) staged a horror show in a dimly lit church abandoned room — putting the audience in an enclosed space, using hidden magic lamps to play realistic ghost images, with a terrifying background sound, successfully creating the "horror theatre" form. Sounds familiar, right? That's right, there were "4D immersive haunted houses" back then — humans don't like to find thrills for a day or two. Robertson used scientific knowledge to improve the magic lamp to have a zoom-like function, making the interaction between ghosts and viewers more spatial, and became famous in one fell swoop.
In the late 18th and early 19th centuries, horror theater performances swept Europe and were associated with mystical forces in folk perception. Taking advantage of people's ignorance, fear and curiosity, some jianghu warlocks and people who claim to have psychics have also used this to deceive and obtain money and reputation.
Robertson's horror show scene in 1797 was no less effective at the time than the current "immersive haunted house", which frightened the audience.
In 1858, the British scientist Henry Dircks developed a new stage technology, through the clever combination of hidden rooms and lights set up under the auditorium, with the help of the "half-transparent and half-reflective" characteristics of glass, so that the actor's figure can "flash" on the stage.
Similar to the magic revealer, Dirkes was unhappy with the prevalence of psychic scams and hoped that through this technology that made it easier to elucidate scientific principles, the public would no longer be blinded by exaggerated performances. He named it "Dircks Phantasmagoria."
In Dirks's design, the theater was illuminated with natural light, which required the entire theater to be rebuilt to achieve a higher cost.
Due to the need to drastically renovate the theater before it could be implemented, Dilkes's idea was slow to open up. But fellow scientist and inventor John Henry Pepper noticed it. Pepperl was also an avid popularizer who recognized the significance of using science to inspire people's wisdom. He simplified the technology so that it could be adapted to most existing theater environments. It is also more famous after Pepperl.com.
Pepper's simplified version is easier to implement and more well known. The ghost of the actor is hidden in the shelter under the stage floor.
Another version of Pepper's illusion. The hidden room is set on the side of the main room, and the glass (green) and the view of the audience (red) are 45°.
It can be said that the two worked together to make Pepper's illusion a success in the market and eventually become a projection technology that has occupied a place in the scientific community to this day. The two reached a brief partnership, but Dirkes gradually criticized it, believing that the balance of fame favored Pepper and ignoring his originality, and criticizing the media and Pepper's school.
In a later book, Pepper affirmed Dirks' important role. Fortunately, the perspective of later generations is more comprehensive, and now the names of the two are usually mentioned together, one is the founder and the other is the reformer.
Now, we can experience the magical effects of Pepper's illusion in specific scenes of many amusement parks. The aforementioned platform shuttle magic, presumably everyone has already glimpsed the beginning - the mirror glass facing the photographer reflects the image of the platform wall, and transmits the scene of tourists entering the tunnel (the light source focuses on the tourist, and the entrance to the tunnel that remains dark becomes invisible), which together form a picture of passing through the wall.
Around the glass, you can see the real platform walls and visitors entering the dark tunnels. Source: TwoWayMirrors.com
In addition to playgrounds and haunted houses, Pepperl's illusion, as a kind of holographic projection technology, is also widely used in various stage performances. We often see singers who are deeply loved but no longer alive return to the scene in this way; Popular virtual characters can also be performed on the same stage as real people.
At the 2012 Coachella Festival, Snoop Dog shared the stage with the late singer Tupac Shakur (right). Source: npr.org
Want to try "holography" for yourself? You can buy or make simple gadgets and use the Pepper Illusion to get a rather three-dimensional projection effect.
Using a mobile phone and this inverted pyramid-shaped device, you can also create a "levitating" image yourself.
How far are we from the "out of thin air" holography in science fiction? Source: Iron Man
Strictly speaking, the Pepper illusion is just a projection technology that can form a holographic-like effect, and true holographic technology is far more complex and more difficult to achieve.
We've all seen holography in science fiction movies—a display or object that is completely suspended in the void, and people can observe and interact with it from any angle. Holography, referred to here, comes from the Greek etymology holo, meaning "total, complete." Ordinary two-dimensional photos only record the intensity information (amplitude) of the light, but do not contain depth information (phase), and visually do not reflect the sense of depth; Holograms contain both, thus reconstructing the stereoscopic image of the object in its entirety and forming a stereoscopic visual effect.
Invented in 1947 by British-Hungarian scientist Dennis Gable and which earned him the Nobel Prize in Physics, the technique was initially used in electron microscopy and later made broader progress thanks to the advent of lasers.
In simple terms, holographic technology is somewhat similar to re-encoding an image. The interference effect of coherent light is involved here.
The laser is divided into two beams by a beamsplitter, one of which hits the object, while the other beam, called the reference light, acts directly on the holographic film, and the two beams of light meet the same frequency, vibration direction, and constant phase difference in the area where they meet, that is, coherent light.
Together, they form a unique pattern of interference fringes on film – the key "code" for recording images of objects. (If you don't have a concept of what interference fringes are, think of the colorful patterns of the oil film being exposed by sunlight.) ）
To unlock the code, the same light as the reference light needs to be hit on the film to produce diffraction, which can reconstruct the stereoscopic image of the object, so that the viewer's eye can receive the virtual image in a false reality.
The process of creating a hologram using the coherent light interference effect. The beamsplitter divides the light into two beams: the light that hits the object and the reference light.
The process of reconstructing the stereoscopic image of an object. Source: Wikipedia
It is not difficult to understand that holographic technology can be seen as a way to store massive amounts of visual information than ordinary photographic techniques. It's just that due to the complexity of technology, cool aerial holograms in science fiction movies are still relatively rare in real life.
Some of the holographic products that people can access now still rely on specific media, such as screens. In this way, compared with the expensive true holographic technique, Pepper's illusion is also the easiest way to "dream into reality".
The seemingly mysterious magic performances of hundreds of years ago have played a role in promoting both science and art today—various early optical devices laid the foundation for the emergence of slide projectors, cameras, and photographic techniques, while the tradition of mysterious and curious performances has been passed down to this day, attracting curious modern people in the form of movies, plays, haunted houses, magical parks, etc.
Some people say that the world of science has no place for magic, but from another point of view, how can science not be a kind of "magic"? With the support of evidence-based theories, turning seemingly impossible things into possibilities and bringing wonderful emotions is the eternal magic of science.
Reference:
https://www.twowaymirrors.com/peppers-ghost-illusion/
https://skullsinthestars.com/2016/12/20/dircks-and-pepper-a-tale-of-two-ghosts/
https://www.vice.com/en/article/z44458/phantasmagoria-were-the-18th-century-suicide-scary-theaters-that-gave-us-movies--2
https://hauntedpalaceblog.wordpress.com/2013/03/17/phantasmagoria-the-eighteenth-century-horror-show/
https://www.boredpanda.com/3d-hologram-smartphone-diy-device-mrwhosetheboss/?utm_source=google&utm_medium=organic&utm_campaign=organic
https://zh.wikipedia.org/wiki/%E5%85%A8%E6%81%AF%E6%91%84%E5%BD%B1
https://en.wikipedia.org/wiki/Phantasmagoria
https://en.wikipedia.org/wiki/Pepper%27s_ghost
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