What are the current methods of hologram technology?

Although three-dimensional images suspended in the air, possessing depth and shape, so the holograms are not entirely real in the way they are constantly depicted in films, various optical technologies exist that can display similar or close three-dimensional images. In this article, I will explain in detail some of the current technological methods and working methods that can create impressive 3D holographic images.

1: Rotating Surface Volumetric Display

In rotating surface volumetric displays, which are quite common in the commercial sector, one or more LED panels or screens rapidly rotate inside a glass-covered volume, displaying images at different times and in different slices. Each angle draws a different 2D layer, and the eye perceives these as a 3D image from a 360-degree angle. However, this method is a type of optical illusion and does not constitute a true hologram.

2: Holographic Fan Blade

Another common commercial product is rotating fan displays. With RGB LEDs arranged end-to-end on their blades, they spin very quickly, and the LEDs flash on and off at just the right time to create a moving image illusion that appears highly detailed and three-dimensional to the human eye.However, this system is essentially two-dimensional and cannot be observed from different angles at the front of the fan.

3: Aerial Plasma Display

The Aerial Plasma Display method is the technology that comes

closest to true holography, capable of creating very small, single-colour, simple moving shapes by using very short, high-energy femtosecond lasers to focus on a point in the air and ionise the air molecules at that point to create a plasma light spot. This technology can create small, simple shapes in the air in a touchable manner, but it is not functional for larger, complex and colourful images due to the high energy required, the danger posed by lasers and the difficulty of processing potentially thousands of points.

4: Pepper's Ghost

The technique known as Pepper's Ghost is the simplest and oldest method and works through a reflection-based optical illusion. An half reflecticve Beam Splitter glass panel placed at a 45-degree angle on a horizo

ntal monitor creates an image that appears to float in the air behind the screen, reflecting a moving object in a dark environment on the screen. Pepper's Ghost is a method that can be easily achieved at home with just a telephone and a simple piece of glass.

5: Light Field Displays

Light Field Displays consist of a layer of micro lenses located in a specific area of an LCD or OLED screen, each directing the light from individual pixels in different directions. By directing the light from t

he pixels at different angles using the light field layer, images appear three-dimensional and depth-rich when viewed from different angles. However, light-field displays only appear 3D within the viewing pyramid covered by the screen surface and, naturally, the image cannot be seen from the sides or edges of the screen; at these angles, depth is lost and the image flattens into 2D.

Today, holograms produced using these technologies cannot create 3D images that float freely in the air like those seen in films, but they are used in many sectors such as the entertainment industry, scientific presentations, and advertising. However, due to the limitations of three-dimensional images created with holograms in every method and their often high cost, AR glasses and similar 3D imaging technologies are more commonly preferred in this field instead of holograms.