Human demand for sound, light, and color has led to the emergence of various information carriers, and display technology has also undergone significant development. Plasma TVs, LED TVs, LCD monitors… these are some of the more familiar mature display methods. In addition, there are some futuristic new display technologies gradually entering our lives.
1. Quantum Dot Display Technology
Quantum dots are zero-dimensional point-like semiconductor materials that possess many novel electronic and optical properties, which can be used in various fields, including display technology. The display technology utilizing quantum dots mainly includes two types: Quantum Dot Liquid Crystal Display (QD-LCD), based on LCD technology, and Quantum Dot Light Emitting Diode Display (QLED), based on OLED technology.
QD-LCD mainly utilizes the photoluminescence principle of quantum dots. The blue light emitted by the LED light source in the backlight module passes through the quantum dot film, where part of it is converted by quantum dots into green and red light. These three colors of light mix to form the white backlight source for the LCD. The green and red light emitted by quantum dots is purer than the light emitted by LEDs, so the addition of quantum dot films allows LCDs to display more realistic image colors and more natural color transitions.
QLED mainly utilizes the electroluminescence principle of quantum dots, where voltage drives the quantum dots to emit red, green, and blue primary colors, and through spatial color mixing, these three colors are converted into various pixel colors.
The light-emitting principle of QLED is very similar to that of the commonly seen OLED screens, only that the light-emitting organic materials in OLEDs are replaced by quantum dot materials. This also gives QLED almost all the advantages of OLEDs, and compared to OLEDs, it has a longer lifespan and brightness. QLED is a more advanced application of quantum dots in display technology.
2. Laser Display Technology
Laser TV, as the name suggests, is a television that uses lasers as the display light source. Due to the excellent monochromaticity of lasers, the color effect of the TV is outstanding. Although called laser TV, this display technology is more like a projector. However, unlike projectors that require a longer projection distance, laser TVs use ultra-short throw projection to project the laser light source onto a light-receiving screen, producing a display effect superior to traditional projectors and TVs.
3. Electronic Paper Display Technology
Electronic paper, also known as electronic ink screen, is a special type of display screen. The images displayed on electronic paper resemble printed pictures on paper. This unique display effect also makes it a potential substitute for paper.
The display of electronic paper mainly comes from the countless ink particles in the middle layer of the screen, which are filled with a transparent base liquid. The base liquid also suspends positively charged white ink and negatively charged black ink, with the size of the ink particles being roughly the same as the diameter of a human hair. When a negative electric field is applied to the ink particles, the white ink moves to the negative electrode under the influence of the electric field, while the black ink moves to the positive electrode. The positive electrode is inside the screen, so the black ink is hidden, and the pixel displays white. Similarly, when a positive electric field is applied, the pixel displays black, and countless pixels combine to form an image.
White and black electronic paper principle diagram
Another special feature of electronic paper is that even when the power is turned off, the distribution of ink on the screen does not disappear. This is a characteristic that no other type of screen possesses, and the brightness of the image will change according to the intensity of the ambient light.
Commonly available on the market is black and white electronic paper, while colored electronic paper is relatively rare. Colored electronic paper either places a layer of color filters above the ink particles or replaces them with colored ink particles, using electric fields to change the position of different colored inks in the particles, which can mix to present various colors.
Future Technology – Glasses-Free 3D Display
Currently, many devices can help us present two-dimensional images in a three-dimensional effect. They all utilize the perception of the human visual system.
The human visual system perceives depth from the multitude of information obtained externally, where the majority of important depth perception elements are two-dimensional, including shadows, perspective direction, relative size, occlusion, and blur. After these two-dimensional depth perception elements are processed by the human visual system, we perceive them as existing in three-dimensional space.
Whether it is painting, photographs, or images, as long as two-dimensional depth perception elements are embedded, the human eye will generate a three-dimensional perception effect; otherwise, optical image illusions will occur. Therefore, a 3D display system must first ensure the above two-dimensional depth perception elements and then add and solve other three-dimensional perception elements, such as stereoscopic parallax, motion parallax, and visual accommodation conflicts, etc. VR is a device that achieves 3D display based on binocular parallax. However, if we want to achieve glasses-free 3D, holographic three-dimensional display may provide us with such an experience.
Compared to binocular parallax, which can cause discomfort such as dizziness, holographic three-dimensional displays can record and restore all the information of the object’s light waves, and the reproduced image has exactly the same three-dimensional characteristics as the original object, resulting in very little discomfort for the human eye.
The development trend of three-dimensional display methods is large depth of field, large field of view, high resolution, and true color real-time three-dimensional display, which is close to or even exceeds the reality seen by the human eye.
Source: Science Popularization China
Typesetting: M
END
Shandong Science and Technology Museum
Shandong Science and Technology Museum