Polarization of light
The asymmetry between the direction of vibration and the direction of propagation is called polarization. It is the most obvious sign that transverse waves are different from other longitudinal waves. Only transverse waves have polarization. . Light waves are electromagnetic waves, therefore, the propagation direction of light waves is the propagation direction of electromagnetic waves. The electric vibration vector E and the magnetic vibration vector H in the light wave are both perpendicular to the propagation speed v, so the light wave is a transverse wave and it has polarization.
Natural light
Natural light, also known as "natural light", is light that does not directly display polarization phenomena. The light directly emitted by natural light sources and general artificial light sources is natural light. It includes all possible vibration directions perpendicular to the direction of light wave propagation, so it does not show polarization. Natural light emitted directly from ordinary light sources is an irregular collection of countless polarized lights, so it cannot be found in which direction the light intensity is biased when directly observed. This kind of light that vibrates with the same intensity in all directions is called natural light.
The vibration direction of natural light is evenly distributed in all directions of the propagation surface, and the effect on the human eye is the same in all directions. [1]
Linearly polarized light
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Light whose light vector always vibrates in a fixed direction is called linearly polarized light. [1]
Elliptically polarized light
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The trajectory of the endpoint of the light vector is an ellipse, that is, the light vector continues to rotate, and its size and direction change with time. Regular changes.
Definition
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The trajectory of the endpoint of the light vector is a circle, that is, the light vector continues to rotate, its size remains unchanged, but the direction changes regularly with time change. The polarization direction of light is evenly distributed as time changes, which can well simulate the isotropic characteristics of the polarization direction of natural light, and the polarization component in any direction maintains a constant size.
The vibration direction of circularly polarized light rotates on the propagation surface, and the overall effect on the human eye is also isotropic.
Circularly polarized light is closest to natural light. [1]
Implementation method
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It is composed of a linear polarizing plate and a quarter-wave plate (a special birefringent material) glued together become. The optical axis of the quarter-wave plate forms an angle of 45° with the polarized light vibration direction of the linear polarizer.
Light: The light incident from one end of the linear polarizer is forward, and the light incident from one end of the quarter-wave plate is reverse. The natural light that hits the circular polarizer in the forward direction becomes circularly polarized light after passing through the linear polarizer and the quarter-wave plate.
Advantages
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Circular polarized light is closer to natural light, which can effectively reduce people's visual fatigue and achieve the purpose of healthy eye protection. [1]
Experimental data
Special research results from Beijing Tongren Eye Hospital, China Institute of Standards, and TCL Industrial Research Institute show that long-term viewing of circularly polarized screens is better than traditional linearly polarized screens. Screens can effectively alleviate vision loss.
Application
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1. Camera filter
A circular polarizer consists of two lenses with a polarizing film sandwiched between them. It can eliminate reflections on the surface of all smooth objects such as water, glass, and metal surfaces, and improve the overall color saturation of the photo to a certain extent. It can also deepen the blue color of the sky on sunny days and improve the contrast. It is an essential filter for landscape photography. [1]
2.3D glasses
3D glasses mainly include linearly polarized 3D glasses and circularly polarized 3D glasses. The stereoscopic effect of linearly polarized stereoscopic glasses is more obvious than that of circularly polarized stereoscopic glasses, but linearly polarized stereoscopic glasses have certain angle factors during viewing, and it is not suitable for head movements such as turning and shaking the head. Circularly polarized stereoscopic eyes are relatively comfortable and have a wider viewing angle than linearly polarized stereoscopic glasses. [1]
3. Display screen
Circularly polarized light can be applied to mobile phone display screens to make the light emitted by the screen closer to natural light and achieve the purpose of healthy eye protection. Among them, Huaxing Optoelectronics’ own patented CPLP circular polarization technology won the National Patent Invention Excellence Award