Polarized light principle

The asymmetry between vibration direction and propagation direction is called polarization, which is the most obvious sign that shear waves are different from other longitudinal waves. Only shear waves have polarization. Light waves are electromagnetic waves, so 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 perpendicular to the propagation velocity V, so the light wave is shear wave and polarized.

natural light

Natural light, also known as "natural light", does not directly show polarized light. 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 propagation direction of light waves, so it is not polarized. The natural light directly emitted by ordinary light sources is an irregular collection of countless polarized lights, and it is impossible to find which direction the light intensity is biased by direct observation. This kind of light that vibrates in all directions with the same intensity is called natural light.

The vibration direction of natural light is evenly distributed in all directions of the propagation surface, and its effect on human eyes is the same in all directions. [ 1]

Linearly polarized light

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The light whose light vector always vibrates in a certain 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 ellipse, that is, the light vector rotates continuously, and its size and direction change regularly with time.

definition

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The trajectory of the endpoint of the light vector is a circle, that is, the light vector keeps rotating, its size remains unchanged, but its direction changes regularly with time. The polarization direction of light is evenly distributed with time, which can well simulate the isotropic characteristics of natural light polarization direction, and the polarization component in any direction remains unchanged.

The vibration direction of circularly polarized light is rotating in the propagation plane, and its comprehensive effect on human eyes is isotropic.

Circularly polarized light is closest to natural light. [ 1]

Realization mode

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It is formed by bonding a linear polarizer and quarter-wave plate (a special birefringent material). The optical axis of quarter-wave plate makes an angle of 45 degrees with the vibration direction of polarized light of linear polarizer.

Light: The light of a linear polarizer is positive, and the light at one end of quarter-wave plate is negative. The natural light emitted to the circular polarizer passes through the linear polarizer and the quarter-wave plate in turn, and then becomes circularly polarized light.

superiority

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Circular polarization is closer to natural light, which can effectively reduce people's visual fatigue and achieve the purpose of healthy eye protection. [ 1]

experimental data

The special research results of Beijing Tongren Eye Hospital, China Institute of Standards and TCL Institute of Technology show that, compared with the traditional linear polarized screen, watching the circular polarized screen for a long time can effectively alleviate the vision loss.

App application

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1. Camera filter

A circular polarizer consists of two lenses with a polarizing film between them. It can eliminate the reflection of all smooth surfaces such as water surface, glass surface and metal surface, and improve the overall color saturation of photos to some extent. It can also deepen the blue of the clear sky and improve the contrast. It is an essential filter for landscape photography. [ 1]

2.3D glasses

3D glasses mainly include wired polarized 3D glasses and circularly polarized 3D glasses. The stereoscopic vision effect of linear polarized stereoscopic glasses is more obvious than that of circular polarized stereoscopic glasses, but there are certain angle factors in the viewing process of linear polarized stereoscopic glasses, which are not suitable for head movements such as turning head and shaking. Circularly polarized stereoscopic eyes are relatively free, and the viewing angle is wider than linear polarized stereoscopic glasses. [ 1]

3. Display screen

Circularly polarized light can be applied to the display screen of mobile phone, so that the light emitted by the screen is closer to natural light, and the purpose of healthy eye protection can be achieved. Among them, Huaxing Optoelectronics' independent patent CPLP circularly polarized light technology won the National Patent Invention Excellence Award.