Smart Vision Lights' Post - smart vision lights llc

 2024-12-01 12:46:56

A collimating lens for a light-emitting-diode (LED) light source is an essential device widely used in lighting engineering. Lens surfaces are calculated by geometrical optics and nonimaging optics. This design progress does not rely on any software optimization and any complex iterative process. This method can be used for any type of light source not only Lambertian. The theoretical model is based on point source. But the practical LED source has a certain size. So in the simulation, an LED chip whose size is 1 mm*1 mm is used to verify the feasibility of the model. The mean results show that the lenses have a very compact structure and good collimating performance. Efficiency is defined as the ratio of the flux in the illuminated plane to the flux from LED source without considering the lens material transmission. Just investigating the loss in the designed lens surfaces, the two types of lenses have high efficiencies of more than 90% and 99%, respectively. Most lighting area (possessing 80% flux) radii are no more than 5 m when the illuminated plane is 200 m away from the light source.

1State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics of the Chinese Academy of Sciences, Xi’an 710119, China

How to collimate a diverging beam oflight

The root cause of dispersion lies in refraction, the bending of light as it travels from one medium to another. However, not all wavelengths of light bend by the same amount. In most transparent materials, shorter wavelengths (blue and violet) refract more than longer wavelengths (red and yellow). This differential refraction is what causes light to spread out into its constituent colours.

Typically, shorter wavelengths (e.g., violet and blue light) have a higher refractive index and thus travel more slowly in a medium compared to longer wavelengths (e.g., red and yellow light). As a result of the higher refractive index, shorter wavelengths bend more (smaller angle of refraction) when entering a new medium than longer wavelengths.

Collimatinglens

Dispersion refers to the separation of white light into its constituent colours (spectrum) due to the different frequencies (colours) of light in a medium, typically a transparent material like glass or water.

Laser collimatinglens

When the frequency of light is closer to the natural oscillation frequencies of the electrons in the medium, the light interacts more strongly and slows down more, leading to a higher refractive index. This is why different wavelengths, having different frequencies and wavelengths, experience different refractive indices and thus refract to different extents.

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Note that colour of light depends on the frequency of light (rather than wavelength). Although the wavelength shortens, the colour of the red light remains unchanged in the new medium (glass).

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Collimated lightsource

The reason for the wavelength dependency of the refractive index lies in the atomic and molecular structure of the medium. When light encounters a medium, the electric field of the light causes the electrons in the medium to oscillate. The extent to which these electrons can oscillate in response to the light depends on the light's frequency (which is inversely related to its wavelength).

Collimatinglensvs focusinglens

White light refers to light that is a combination of all the visible colours of the spectrum. In a sense, it's a mixture of various wavelengths of light that human eyes can detect, ranging approximately from 400 nm (violet) to 700 nm (red).

Snell's Law relates the angle of incidence and the angle of refraction to the refractive index of a medium. It's given by:

Collimatedbeam

A beam of white light goes from air into flint glass at an incidence angle of of 43.2º . Refractive index of flint glass for red and violet light are 1.662 and 1.698 respectively.

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The refractive index of a medium isn't a constant value but varies with the wavelength of the incoming light. This variation is particularly noticeable in transparent materials like glass or water.

The velocity of light changes with the medium it propagates in because its wavelength changes (frequency remains constant).

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