As with all technologies, the history of projection is the story of the culmination of many individual advancements in the arts and sciences. From the earliest shadow plays on the cave walls of antiquity to 360° projection domes, humans have been enchanted by light and color and driven by the desire to share stories, ideas, and experiences.
Even with all the incredible progress of the past few centuries, we exist in a time when the capabilities of human technology allow us to express our creative ideas in ways unimaginable to us as recently as 20-30 years ago. Projection, from the Latin proicere, or “throw forth” is defined by the Oxford dictionary as “the presentation of an image on a surface.” Other definitions follow a similar vein, but almost all omit the most important element: light.
NATURAL PHILOSOPHY AND OPTICS
New optical technology wasn’t just accelerating humans’ ability to create a spectacle, it was advancing our knowledge of the inner workings of the universe. New glass-making techniques using lead resulted in optically clear, low-dispersion lenses and prisms. More than just the inventor of one of the most popular projection systems of all time, Christaan Huygens was a Natural Philosopher who, with his 17th-century contemporaries, sought to explain the inner workings of the world. Huygens and others observed the reflections, diffractions, and refractions of light and proposed that light was a wave, a luminiferous ether that spread out from its source in all directions.
Famed English Physicist Isaac Newton disagreed, believing that if light traveled in a straight line, then it could not be a wave. Newton observed the way a prism of glass separated a beam of light into a distinct spectrum of colors and concluded that this separation could only occur if light was made of incredibly tiny particles, or corpuscules. The two opposing schools of thought went back and forth for centuries, but the mystery persisted.
Newton’s experiments with prisms also demonstrated one of the inherent challenges of producing a clear optical image with glass lenses, chromatic aberration. Since the color separation that occurred with the glass optics of his telescope interfered with his astronomical experiments, he constructed a telescope made of mirrors instead. This, in turn, inspired Swiss Astronomer Leonhard Euler’s Episcope in the mid-18th century. It is also known as an opaque projector, because instead of focusing a beam of light through a translucent medium, it illuminated the surface on which it sat. A hole in the bottom meant the episcope could be placed over any image or object, then a mirror at the top would reflect the image of that object through a lens to create an enlarged, albeit dim projection.
IMMERSIVE PROJECTION EXPERIENCES
CRT projectors were not bright enough to replace film projectors in most situations, but the situations and ways in which projectors were used continued to grow. In 1969, Disneyland’s Haunted Mansion became the first projection mapping experience. Using 16mm footage of ghostly faces on a black mat background to selectively illuminate a physical counterpart in space, it created an ethereal illusion that had never been seen before. Projection elements have been a part of amusement park rides ever since.
IMAX projection, developed in the 1960s, also immersed its audience by covering as large an area as possible with light. The IMAX format turned the image frame sideways and ran its 70mm film horizontally to maximize the picture. The gigantic projector emerged from the floor in the middle of a large dome, much like a planetarium, and an ultra-wide lens threw the image onto every part of the enormous curved surface. The audience seated below saw an illuminated image that filled nearly their entire field of view, and the movement at the periphery of their vision made for one of the most thrilling projection experiences yet.
A much less bulky projection system was also being used to create immersive experiences of an entirely different sort. The overhead projector developed by the US military in WWII used a mirror and condenser lens to project translucent images that are placed on top of a backlit Fresnel lens. The Fresnel lens, invented by the French physicist of the same name, uses concentric rings to gather a light source into a concentrated beam. Since 1827, the bulky glass versions have been used in lighthouses and high-powered searchlights. A smaller, thinner, rectangular version was developed as a screen for CRT projection televisions, and the same materials soon became a surface for live-projected content creation. Images and documents could be printed onto transparent plastic sheets, but they could also be written on directly.
What Is Holographic Projection?
Despite its futuristic appearance, holographic projection has been around since the 1940s—the term “hologram” was actually first coined by Hungarian/British engineer Dennis Gabor back in 1949. Holographic projectors essentially provide either a two-dimensional or three-dimensional projection which can be seen without any additional equipment (such as cameras or glasses).
Used well, holographic projection technology can provide a stunning visual experience—whether it’s simple ‘Pepper’s Ghost’ style effects, the late Bob Hope re-appearing at the 83rd Oscar’s, or Halsey performing ‘Without Me’ underwater at the 2018 MTV EMAs.
Let’s explore what holographic projection is, how holographic screens work, and where they can be put to use for the greatest possible effects.
How Holographic Screens Work
Creating a hologram effect on a large scale can not only be an incredibly costly undertaking, it can also require a huge amount of space to work effectively. Alternatively, pairing a holographic screen with a standard projector is a great way to create a holographic effect without the hefty price tag.
There are two main types of holographic projection screen: front and rear. Let’s explore how both of these work in more detail.
What is throw distance for a projector?
A projector’s distance from the lens to the screen surface is called the Throw Distance. The throw distance and the size of the image it produces on the screen are proportional to each other based on the optics of the lens. As you increase the distance between the projector lens and the screen the image will also increase.
How far do you put a projector from the screen?
A projector’s distance from a screen and the size of the image it produces are proportional to each other based on the optics of the lens. As you increase the distance between the projector and a screen the image will also increase. If your projector has a zoom lens, the lens can be adjusted to change the size of the screen image without changing the distance of the projector. Since each projector lens is different, an online projection calculator tool will help you calculate the size of an image on a screen relative to how far the projector is placed from screen.
What is a throw ratio for a projector?
For any given projector, the width of the image (W) relative to the throw distance (D) is know as the throw ratio D/W or distance over width. So for example, the most common projector throw ratio is 2.0. This means that for each foot of image width, the projector needs to be 2 feet away or D/W = 2/1 = 2.0. So if I’m using a projector with a throw ratio of 2.0 and I have an image width of 5 feet, then my throw distance must be 10 feet. So the throw ratio is a simple formula that let’s you easily compute throw distance or image width given that you know one of these measurements. A projector zoom lens will have two different throw ratios, one for the minimum zoom setting and one for the maximum zoom setting.
What is considered a short throw projector?
A short throw projector is a projector with a lens that has a throw ratio of 0.4 (distance/width) or less. These projectors are ideal for rear screen applications where the area behind the screen is limited, or for a wall mounted application where the projector will be mounted within 1 or 2 feet from the screen. The goal of these projectors is to produce as large of an image within the shortest amount of space between the projector and the screen.