Principle of sunglasses

High quality sunglasses produced by the sunglasses factory are very effective “light regulators”. Sunglasses can adjust external light to fit the human eye. In the next section, we will introduce the various light adjustment techniques used by Sunglasses manufacturers. In order to better understand these technologies, we must first understand some knowledge about light.

A light wave has certain electromagnetic energy. The size of a wave is measured by its wavelength. Visible light has a wavelength range of 400 to 700 nanometers. The energy of light wave is inversely proportional to the wavelength. The shorter the wavelength, the higher the energy. In the visible light, the purple light has the largest energy, the red light has the smallest energy, and the ultraviolet light is above the visible light spectrum. In fact, natural light contains a lot of ultraviolet light. Due to the high energy of ultraviolet rays, ultraviolet rays can damage your cornea and retina. What is glare?

The unit of measurement of the brightness or intensity of light is the lumen. For example, indoors, most artificial light has an intensity of 400 to 600 lumens. If it is sunny outdoors, the brightness will fluctuate in a large range. The brightness in the shade is 1000 lumens, while in places with large cement fields such as highways, the brightness is 6000 lumens. Below 3500 lumens, our eyes feel comfortable. When the brightness of direct or reflected light reaches 4000 lumens, the human eye begins to struggle to receive light.

When we try to look at these bright areas, we only see a white flash, which is glare. In order to reduce the discomfort caused by the large amount of light entering the eyes, we began to squint. Once the brightness reaches 10000 lumens, your eyes begin to filter out the light completely because the light received is too strong. Exposure to such intense light for too long can cause damage, leading to temporary or even permanent blindness. On a clear day, the light reflected by a large area of snow can be as high as 12000 lumens. If we look at the light directly without any protection measures, it will lead to “snow blindness”.

Visible light is light that the human eye can detect. The visible light we see from the sun looks colorless, which is what we often call white light. In fact, it’s a mixture of colored light of many frequencies. In the spectrum range of visible light, all colored light mixed into the light is colorless, that is, white. (for more information, see how light works).

We have two basic ways to see colors. One way is that an object itself can emit light of a certain frequency, for example, neon lights show color in this way; the other way is that the object absorbs all other frequencies of light, and only reflects a certain frequency of light, or reflects multiple frequencies of light. These light waves are mixed to be perceived as one color of light. For example, objects coated with paint show color in this way 。 For example, to see yellow light, one way is that the object directly emits light of yellow frequency; the other way is to absorb the blue part of the spectrum and reflect the red and green part of the light. After mixing these two kinds of light, the human eye can perceive it as yellow light.

When talking about the light associated with sunglasses, the following three types of light are important:

Direct light – direct light is the light that comes directly to your eyes from a light source, such as the sun. Too much direct light can blur the details of the surrounding environment and make it difficult for you to focus.

Reflected light – reflected light often exists in the form of glare. Reflected light is the light reflected back to the eye from a reflecting object. Like direct light, strong reflected light makes it difficult to perceive details or look directly at an object. Snow, water, glass and white sand are good reflective surfaces.

Diffuse light – diffuse light is light that bounces off and spreads in many directions, so it does not appear to have a specific light source. A typical example of diffuse light is the glow over big cities. It is difficult to identify a single light source for it. In the absence of a direct light source, we can still see things, which is the credit of diffuse light.

High quality sunglasses eliminate ultraviolet light from the spectrum, reduce direct light, make people feel comfortable, and also eliminate or reduce reflected light (depending on the reflector).

One interesting property of light is polarization. When reflected from certain surfaces, such as water, light polarizes. Due to the polarizing properties of the reflected light, polarized sunglasses can eliminate the light reflected from the water surface or similar reflecting surface.

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