Polarized sunglasses are sunglasses. Polarization can be divided into three types, namely, linear polarization, elliptical polarization, and circular polarization. Generally, the so-called polarized light refers to linear polarized light, also known as plane-polarized light. The vibration of this kind of light wave is fixed in a specific direction, the propagation path in space is a sine curve, and the projection on the plane in the vertical propagation direction is a straight line.

The plane composed of the vibration direction and the propagation direction of linear polarized light is called the vibration plane, and the plane perpendicular to the vibration direction and containing the propagation direction is called the polarization plane. Through polarized sunglasses, natural light can obtain linear polarization, which is often used in the research of crystal optics.

Because of the function of polarizing light, polarized sunglasses can block all harmful light without affecting the transmission of visible light, and can protect the eyes. In addition to the basic anti-ultraviolet function, polarized sunglasses also have anti-glare, reflected light on the road surface, scale light on the water surface, and are suitable for driving, fishing, tourism, and daily wear.

Polarized sunglasses can block the uncomfortable strong light and protect the eyes from ultraviolet rays. This is due to the metal powder filter device, which can "select" the light when it enters. Polarized sunglasses can selectively absorb part of the wave bands that make up the sun's rays because they use very fine metal powders (iron, copper, nickel, etc.).

Polarized sunglasses provide another mechanism to protect the eyes. The reflected light of the asphalt road is a special polarized light. The difference between this reflected light and the light directly from the sun or any artificial light source lies in the problem of order. Polarized light is formed by waves that vibrate in all directions, while ordinary light is created by waves that vibrate in all directions. This is just like a group of disorderly people walking randomly and a group of soldiers marching with neat steps, forming a sharp contrast. Generally speaking, reflected light is a kind of orderly light. Polarizing lenses are particularly effective in blocking this light because of their filtering effect. This kind of lens only allows polarized waves that vibrate in a certain direction to pass, just like "combing" light. For the road reflection problem, using polarizing sunglasses can reduce the transmission of light, because it does not allow light waves that vibrate parallel to the road to pass through. The long molecules of the filter layer are directed horizontally and can absorb horizontally polarized light. In this way, most of the reflected light is eliminated, while the overall illumination of the surrounding environment is not reduced.