In this blog post, we will take a look at how far transparent display technology has actually progressed, as well as its principles and potential.
A feast for the eyes: the science of displays
Have you ever seen the movies Iron Man, Kingsman: The Secret Service, or the TV series Sherlock? Watching the high-tech devices used by the main characters in these works, you may have thought, “I want to try that too.”
In particular, special glasses and helmets that share the user’s field of vision and provide useful information such as the weaknesses of opponents immediately catch the attention of viewers. What if “smart glasses” that incorporate all the functions of a smartphone, just like the glasses in the movie, were actually released? They would probably sweep the market in no time. Even I would like to buy a pair, even if they are a little expensive.
Surprisingly, this imaginary technology is no longer just a fantasy. Transparent displays are already being actively researched and developed. As the name suggests, this technology uses a material as transparent as glass to function as a display. It is innovative in that it not only displays colors and shapes in a fixed manner like colored glass, but also allows the viewer to see through it while freely displaying colors and images digitally.
Two faces of transparent displays: projection type and direct view type
Transparent displays are broadly divided into two types: projection type and direct view type.
First, projection type displays operate on a principle similar to that of a projector beam. This type is further divided into HUD (Head-Up Display) and HMD (Head-Mounted Display).
HUDs project strong light from outside onto glass, and some of that light is reflected off the glass and into the user’s eyes. However, because of the low reflectivity of glass, the light source must be very bright, and the screen is only visible when there is a lot of ambient light, so HUDs are only effective outdoors. Naturally, they consume a lot of energy and are not very economical.
HMD does not reflect light onto glass, but projects it directly into the user’s eyes. In theory, this is a much more efficient technology, but because it involves projecting light directly into the eyes, there are significant safety issues and technical difficulties, and it is still in the active research stage.
The pinnacle of technology: direct view displays
The true pinnacle of transparent display technology is the direct view display. This type of display is transparent and can control the transmittance (how much light passes through) at specific locations. In other words, it is possible to display images or text in specific areas while keeping the rest transparent.
If this technology is commercialized, the “transparent smartphone” used by Tony Stark in the movie could become a reality. However, finding a material that is transparent and allows for free adjustment of transmittance and color has not been easy.
Moving colored glass, electrochromic materials
Electrochromic materials were developed to realize this technology. These materials, which are made of oxides of certain metals, have the property of changing color and transmittance when electrically stimulated, causing an oxidation-reduction reaction inside the material.
For example, once the color and transmittance are set at a specific location, the state can be maintained without additional stimulation. Therefore, energy is only required to operate the display when changing colors or adjusting the transmittance. Due to this characteristic, electrochromic materials are sometimes described as moving colored glass.
Of course, there are still many technical issues to be resolved, such as pixel sensitivity control, sharpness improvement, and response speed enhancement, but the possibilities are endless.
How far will the pleasure of seeing evolve?
In fact, humanity has long pursued the pleasure of seeing. Starting with prehistoric cave paintings, we expanded our sensory realm by engraving patterns on pottery and glass and painting landscapes on canvas. Eventually, we captured reality in photographs, and now we have reached an era where screens are “floating in space.” Transparent display technology goes beyond mere convenience to open up a new visual experience that expands the human senses.
Although there are still technical challenges to be overcome, it is clear that this technology will become part of our everyday lives in the near future. In an era where the joy of seeing is the joy of living, display technology is quietly evolving to make our daily lives richer and more vivid.
