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Karagoz
How does AR coating works on cameras?
How do they decrease reflection?
And how does it improve the quality?
How do they decrease reflection?
And how does it improve the quality?
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It's a clever system and this is the simplest form of it. There is a thin coating of a substance with a refractive index that is less than the glass. The thickness is a quarter wavelength and the light that is reflected at the first surface is canceled buy the light reflected by the second surface, which is a half wavelength delayed. So, at one wavelength, at least and for light at normal incidence, there is no reflection and all the light goes through.Karagoz said:How does AR coating works on cameras?
How do they decrease reflection?
And how does it improve the quality?
Karagoz said:How does AR coating works on cameras?
sophiecentaur said:It's a clever system and this is the simplest form of it. There is a thin coating of a substance with a refractive index that is less than the glass. The thickness is a quarter wavelength and the light that is reflected at the first surface is canceled buy the light reflected by the second surface, which is a half wavelength delayed. So, at one wavelength, at least and for light at normal incidence, there is no reflection and all the light goes through.
In real life, they use several layers with different thicknesses and materials to spread the 'blooming' effect over most of the visible bandwidth.
Google "Anti reflection coating lenses". This wiki article will start you off in the right direction.
Quality is improved because more light gets through and, at the same time as letting more light in, there are fewer multiple reflections and less flare. Early cameras had no such coatings and the excellent pictures that were taken with some cameras needed very well controlled lighting conditions and angles to avoid these reflection problems.
The energy has to go somewhere (conservation) so it goes through.Khashishi said:When you have destructive interference in the reflection, you have constructive interference in the transmission.
sophiecentaur said:The energy has to go somewhere (conservation) so it goes through.
Flare is reduced because any (already low level) internally reflected goes out at the next surface it meets.
I think you should show evidence that you have actually researched this yourself. You are simply repeating your initial question. PF doesn't work like that.Karagoz said:How does the energy go through the lenses?
Why and how the internally reflected goes out at the next surface it meets?
Karagoz said:How does the energy go through the lenses?
Karagoz said:Why and how the internally reflected goes out at the next surface it meets?
I know that is the usual answer but the significance of SNR is 'logarithmic' and AR coating will only improve SNR by perhaps 1dB or so, which represents a very small difference in exposure required. I think the overwhelming advantage is in the improvement of picture 'sharpness' due to increased contrast as flare etc. is reduced. Replacing the good quality Kit Lens that came with your camera, with a super dooper equivalent lens will improve the contrast and, possibly, sharpness of your pictures.Drakkith said:The increase in the intensity of the light that makes it through the camera lenses, along with the reduction in the stray light, increases the signal-to-noise ratio of the resulting image. More light = more signal, less stray light = less noise.
sophiecentaur said:I know that is the usual answer but the significance of SNR is 'logarithmic' and AR coating will only improve SNR by perhaps 1dB or so, which represents a very small difference in exposure required. I think the overwhelming advantage is in the improvement of picture 'sharpness' due to increased contrast as flare etc. is reduced.
Drakkith said:In the form of EM waves. The waves destructively interfere in one direction and constructively interfere in the other. Wave interference is the crux here, and you can't understand this without getting into the details of interference.
Drakkith said:. . . Then, when this internally reflected wave hits the medium boundary again, most of it passes through with very little reflected. The part that passes through simply leaves the system (since it just passed back out of the first lens of the system).
Ha ha, you have asked the question that challenges the simple explanation. There are in fact many reflections between the layers and the 'through' ray is enhanced by interference from the other internal bounces, resulting in all (most) the light being transmitted. The layer has the effect of cancelling all reflections from both surfaces. If the angle of incidence is not zero then this process will not work as well and this will result in a colour caste of the surface as some wavelengths are reflected more than others.Karagoz said:But only one wave is passing through the glass. How does it interfere with another wave to make a constructive interference?
I think it is more of an effect of modifying the transfer function of the lens than the effect of random noise. There will be a noise-like effect, rather like the quantisation 'noise' in a digitised signal which is really a form of distortion. It takes contributions from other parts of an image and puts them into other parts.Drakkith said:True, the increased contrast is the most noticeable improvement (though even this is related to the SNR).
sophiecentaur said:I think it is more of an effect of modifying the transfer function of the lens than the effect of random noise. There will be a noise-like effect, rather like the quantisation 'noise' in a digitised signal which is really a form of distortion. It takes contributions from other parts of an image and puts them into other parts.
Karagoz said:From what I know, to make interference happen, it must be two waves in phase that move into same direction.
Karagoz said:In this model, they show one wave that reflect two times, and each is interfering with each other, and cancelling each other (destructive interference).
Karagoz said:But only one wave is passing through the glass. How does it interfere with another wave to make a constructive interference?
Karagoz said:If I understand you correctly, you mean: most of the waves that hits the medium boundary between the coat and lens do reflect again, and these reflected waves then hits the boundary between coat and air, and then moves out to the air?
Interference and AR coatings are used to minimize reflections and increase the transmission of light through a surface. They are commonly used in optical devices such as lenses and mirrors to improve clarity and reduce glare.
Interference coatings work by layering materials with different refractive indices on a surface. This creates a thin film that reflects certain wavelengths of light while allowing others to pass through. AR coatings use a similar principle, but are designed to reduce reflections at a specific wavelength or range of wavelengths.
No, interference and AR coatings can be designed for a range of wavelengths, including infrared and ultraviolet. They can also be used for other types of electromagnetic radiation, such as radio waves.
Interference and AR coatings are typically applied using a vacuum deposition process, where the materials are heated and evaporated onto the surface. This creates a thin film that adheres to the surface and produces the desired optical properties.
Yes, interference and AR coatings can be removed by using chemical or mechanical methods. They can also be altered by changing the materials or thickness of the layers, which can change the optical properties. However, these processes can be complex and may affect the overall performance of the coating.